Every tradition, be it a Gifted or unGifted one, has a different way of handling Warping Points. Hermetic Magi undergo Wizard's Twilight, Folk Witches go through the Witch's Moon, Amazons suffer through the Sacred Sickness, and Sahirs have Fatra Beyna.
First, if a magician decides to change his tradition and complete all the possible integrations to do so, can he change the way he handles Warping, from his old tradition's to the new one?
Second, if two magicians from different traditions decide to cooperate with each other and train together an apprentice in both tradition's ways, how is it determined which way of handling Warping the apprentice ends up with?
RoP:D states that Hermetic magi with Holy Methods and Powers may undergo either Wizard's Twilight or Divine Ascension, whatever feels more appropriate to the troupe... so I guess there's no hard and fast rule, and in particular no prohibition to "switch" if it makes sense in-story.
Twilight/Divine Ascent are top tier.
Infernal warping/Other magical traditions may have an order, but it's not specified afaik.
Faerie warping is bottom tier.
Integrating a different form of warping while keeping all the Hermetic powers would be a great breakthrough.
It also states that, "once the choice is made, it cannot be changed". This could be taken as evidence that while a starting Hermetic Magus with True Faith or Holy Magic may select either Wizard's Twilight or Divine Ascension, characters must otherwise stick with the first Twilight variant they are exposed to - Faerie Calling being the sole exception in that all other reaction to Warping (save the generic one suffered by mundanes) explicitly take precedence over it.
I interpret it, additionally, as "a Hermetic Magus who develops Holy Magic midgame may turn Ascentward if it fits the story," because most Holy Magi are converted Hermetics rather than being apprenticed to other Holy Magi. But the choice has to be made when developing Holy Magic.
Other than that exception, however, I'd say "stick with your first Warping." Fatra Bayna etc. are equivalent to Twilight in this.