what about drop rates for the items that come from cards? Like myst case/raydric archer cards, afaik those don't get increased by anything
This is correct, the code for drop calculations was recently published and ore discovery and special drop items use a different table that is checked after drop multipliers are accounted for on the monster's main drop table. Technically MvP rewards are the same as well, they could actually modify the treasure boxes to be MvPs that award god item components at a 0.8% and that wouldn't be modified by gum.