OK, finished it with 100%. Thankfully the speed trials aren't required to 100% all the maps.
Aaaaand. God damn them for that ending. It's a good ending but damn man...
Now that I've finished. The movement in this game is sublime and so fluid and responsive. It's going to be difficult to play another platformer right after this, so I'm not going to play another platformer for a while.
Boss fights become significantly easier if you work at getting as close to 100% on each map as you can given the movement abilities you have unlocked to that point. So, if you don't want the game to become too easy, don't be a completionist until closer to the end. Alternatively if a boss is proving difficult, go hunting for collectables and spirit light.
Regards,
SB