Hopper becomes effectively full around Amethyst+. I can’t benefit from upgrades such as Topaz Affinity since my hopper never clears and no Topaz Coins can count toward the upgrade buff.
EDIT: Turns out there’s a nifty control UI to the hopper now. Upon tilting fully to the side, I’m able to dump the near-worthless coins in favor of the high-value ones I’ve unlocked. Cool feature, thanks.