Welcome to the boards!
There are so many variables for a Troupe - playstyle, high-/low-fantasy preference, social/wilderness locale, freedom of action, etc etc. And then AM-specific elements - the Fae Realm, Hermetic politics, new vs. established Covenants, etc etc. At one level, anything can be anywhere, but at another diff Tribunals do tend to lend themselves better to one or another...
Stonehenge tribunal -
One of the more "wild west" of the Tribunals. Isolated and isolationist, it often sends no delegation to any Grand Tribunal - it minds its own business, and prefers the Order to do likewise. But several large Covenants tend to dominate the Hermetic political scene - hard to appeal for "justice" if you don't invite that Law at other times. Local politics are interesting if you want to go there - Anglo-Saxon vs. Norman French vs. Welsh, etc. Old stone henges and dolmens, iron-age hillforts and Roman ruins mixed with little "modern" castles everywhere. Classic stuff - and most English-speakers will recognize parts of the history if you want to insert it.
Greater Alpine -
Nice and central to all of Europe, with several central (Roman) roads that lead to adventures anywhere. THE central crossroads of Europe, for more far-reaching adventure hooks. If not on a main road, there are some hidden valleys and backwaters in the Alps off the trail. Snow and ice and mountains, sealed up in the Winter, but green meadows in the Spring. Politics tend to be old and conservative (to the point of discouraging "new" Spring Covenants), so the PC's would probably(?) be joining an existing one - altho' exceptions always exist.
The Black Forest - need we say more? Magical critters and locales, the Fae. Uncharted wilds, majestic and far-reaching rivers, isolated castles, or great cities if you want them. Order of Odin to the north.
Very crowded (in a Hermetic sense). Mundane politics, mundane neighbors, mundane wars. The Church, and church politics. Paris, in all her 100,000-population glory. Virgin wilderness and new vis sources are hard to find, and Tribunal matters are often ones of disputed claims of territory, influence or interference. (Note that "mundanes" can be gateways to the supernatural - the Infernal, the Divine, non-Hermetic traditions, court magicians, etc. etc.)
I'll bring up another factor - languages. If you play "realistically", then there are many, many languages across Europe, and things like "French" or "German" or "English" simply don't exist at this time. Stonehenge has 3 basic languages (Anglo-Saxon, Norman French, and Welsh) until you get up toward Scotland - this may be one of the fewest. (The Alps has only three also, Alpine-specific versions of German, French and Italian, but then the roads lead directly to a spectrum of other tongues.) Stonehenge also has harder boundaries, the water discouraging travel outside the immediate locale.
Otoh, if you handwave that all away - nm.
Here's the "official" spiel from the downloadable 4th ed pdf - things haven't changed that much...
(I'll just copy/paste the whole thing and highlight the ones you named - easy enough.)
The Hibernian Tribunal, which consists of Hibernia and some nearby islands, is a small tribunal at the edge of Christendom. The land is wild and magical, and most magi live in isolation from the population of the land. Nevertheless, because of the relatively small size of the tribunal, a great percentage of the magi in the tribunal are involved in tribunal politics.
The Loch Leglean Tribunal covers Scotland and the northern islands. This area is also highly mystical, and has the distinction that the local populace is generally more accepting of magi than folk are elsewhere. The majority of magi here are of House Ex Miscellanea. A great wealth of information about the Loch Leglean Tribunal can be found in the Ars Magica supplement Lion of the North.
The Stonehenge Tribunal covers England and Wales. The domus magna of House Ex Miscellanea, Cad Gadu, is located in this tribunal. The Stonehenge Tribunal is disorganized, in part because many of the tribunal’s magi live in isolation, and in part because of the rapid clearing of land and forest deprive them of the opportunity of live apart from society in magical areas.
The Iberian Tribunal covers all of the Iberian peninsula, including land currently held by the Moors. The politics of the Iberian Tribunal are chiefly concerned with the Reconquista, though there is certainly nothing that could be called agreement among the magi. At least two covenants routinely side with the Moors against the Christian forces. Although conflict is common, many covenants have a great wealth of both mundane and occult knowledge, plundered from conquered Moslem libraries and gained from Moorish scholars. You can find more information in the Ars Magica supplement Iberia.
The Normandy Tribunal covers France, including Burgundy and the Low Countries. It is home to Fudarus, the domus magna of House Tytalus. As the land here becomes more and more crowded with mundanes and the influence of the Dominion, the covenants of the tribunal must become more and more hidden and isolated. Remaining apart from the mundanes becomes a more difficult task with each passing year.
The Provençal Tribunal covers Languedoc, including Gascony and the Pyrenees. It contains Val-Negra, the domus magna of House Flambeau. The Provençal Tribunal is the cultural center of the Order, and perhaps its political center as well. Magi of Jerbiton are quite active here, and so relations with the mundanes are quite good. Many old and powerful covenants are found within this covenant.
The Rhine Tribunal consists of the lands of the Holy Roman Empire north of the Alps—Germany and the Rhine valley. Within its boundaries lie Durenmar, domus magna of House Bonisagus; Crintera, domus magna of House Bjornaer; and Irencillia, domus magna of House Merinita. Once the center of the Order, the Rhine Tribunal’s power has decreased as the area has become more and more densely populated with time’s passage. Some magi have started to involve themselves in the politics of the Empire, much to the displeasure of the quaesitores.
The Tribunal of the Greater Alps holds sway in the region around the Alps, including Bavaria. It is home to Valnastium, domus magna of House Jerbiton, and the Cave of Twisting Shadows, domus magna of House Criamon. The old covenants of this tribunal strictly enforce the status quo, allowing no new covenants to be formed within its borders. This lends the tribunal peace and stability, which its members enjoy.
The Roman Tribunal covers the southernmost portion of the Holy Roman Empire—the Papal states, the Kingdom of Naples, Sicily, Sardinia, Corsica, and even has one covenant in North Africa. Harco, domus magna of House Mercere; Magvillus, domus magna of House Guernicus; and Verdi, domus magna of House Verditius are found here. This is the tribunal where magi are most involved in the world— living in cities, having political relationships with aristocrats, and selling their magical wares to mundanes. Most of the members of the Order here are quite cosmopolitan, and spend a great deal of time in the great cities. Some do not belong to covenants, or do so only in name. Relations among the covenants and magi are a nightmare mass of Byzantine political machinations. More information can be found in the Ars Magica supplement Rome.
The Tribunal of Thebes consists of the Byzantine Empire—Greece, Asia Minor, and the islands of the Aegean Sea. This tribunal includes the great city of Constantinople; one covenant is even found within its walls. The lands of Greece, though they fell from glory long ago, still have a great deal of magic to offer to those who live here.
The Transylvanian Tribunal consists of the kingdoms of Bulgaria and Hungary. The domus magna of House Tremere, Coeris, is found here. This area is perhaps the most magically potent of the tribunals, for the power of the Dominion is still quite weak. Although this makes the Transylvanian Tribunal one of the fastest growing in the Order, it also means that outside magical threats also abound. The Tremere have total political dominance in this tribunal.
The Tribunal of the Levant governs the magi of Christian Palestine, as well as a few covenants scattered throughout Egypt, Asia Minor, and Syria. The covenants of this tribunal have managed to find great knowledge both in the remains of earlier civilizations and in the Muslim scholars and sorcerers who live in this area.
The Novgorod Tribunal is the farthest eastern tribunal in Christendom. It consists of the Kingdom of Poland and the Russian Principalities, as well as the Nordic and Slavic lands of the North. Vast amounts of unsettled land and little competition among Hermetic magi for magical resources make this area attractive, but problems with pagan wizards and Mongols can be severe.