Though there are only two main deck monsters that players actually play on the field Raye and Roze the Link monsters such as Hayate, Shizuku, Zeke, and Kagari carry the engine forward
From my experience, Brawl is perfect when you want to jam quick games, experiment with new commanders, or test synergies with digitalonly cards
Voice has also appeared in Collected Company decks in Modern, as it's a wondeful target, and was a staple of Birthing Pod decks before Pod was banned, because it could be sacrificed to Pod and still leave something behind.
Every other card in the standard portion of Shining Fates is currently worth under $20.00
The rainbow cards are colorful additions to any TCG set, but they lack the beauty of alternate art cards, which is why they do not have the same price ceiling
As we get more spoilers revealed, I'll update this list