I am actually pretty adept at converting characters. 4th edition characters often seem powerful compared to 5th edition expectations, but really this only is obvious with older characters (30+ years as a magus), and it is theoretically possible for a 5th edition character to progress at a similar rate.
You basically have to ignore the reccomended Virtue and Flaw restrictions, and you have to double check all of your spells. Once you convert one or two it gets easier, because you have converted versions of spells unique to your saga to build from.