For example, Paragon Surge, would it change it to +4 +4 rather than +2 +2?
Our DM allows Arcanists to pick up Arcane Discoveries. How would it play with a Brown Fur Transmuter. Would a Fox's Cunning go up to +8, would Paragon Surge go up to +4 +6. At 20th level would it go up to +12 or to +6 +10?
Other transmutation spells with multiple ability enhancements?
Looks to me like each and every ability enhancement gets the Idealize boost, and it should be cumulative with BFT's Powerful Change.
At 20th Paragon Surge is getting +0 +2 from BFT and +4 +4 from Idealize, so +6 +8 total unless I'm missing something. Not sure where you're getting the +12 or +6 +10 possibilities from.