Snatch and Vlad will increase the chance of getting 4 gold chests rather than 3 gold chests. With no buff you'll get 3 chests pretty frequently, while with high buffs you'll usually get 4.
so 4 gold is mostly expected, that makes a big difference.
considering i did find a few accessories with drop rate increase, i wonder if that'd push it to a guaranteed 4... (would have to stick them on some SR girls or something though)