QIf I summon a Hishi Miracle with this follower's Fanfare ability, then evolve Hishi Miracle, at the start of my end phase, do "return this card to its owner's hand" and "if there are at least 9 faceup cards named Carrot in your evolve deck, each opponent buries the top 20 cards of their deck" both trigger?

AYes. They both trigger and may be resolved in any order. Note that even if you choose to return Hishi Miracle to hand first, you still resolve the "each opponent buries the top 20 cards of their deck" ability.

QIf I summon a Marvelous Sunday with this follower's Fanfare ability, then return this follower to hand with Marvelous Sunday's Fanfare ability, do I still have to return Marvelous Sunday to hand at the start of my end phase?

AYes, you do.