The only REQUIRED raids for MSQ are the Crystal Tower(CT) Alliance raids. But...they're are only raids in name only. They are so easy to steamroll because level sync, by itself, doesn't hammer our stats down enough to prevent the raids from being steamrolled so easily when the majority of the dpses have such game-breaking-good endgame equipment. If you're feeling nervous about them you can just watch a guide to be aware of what will one-shot you. It's just a few things. Like, King Behemoth's meteor if you don't hide behind boulders, Amon's Curtain Call if you don't hide behind a frozen player, etc.

MSQ Trials and Normal Raids are basically the same thing. The only real difference is MSQ trials are from MSQ missions and Normal Raids are the side content with separate stories. They're both fancy 8-player boss fights.