I have a Deck and love it. I also have a Dock, but I don't use it that often other than as a glorified charging station. Not because it doesn't work (it works great), but just because half the point of the Deck is so I can game on the couch while my wife watches a show or whatever.
I also have
EmuDeck installed and have used it to emulate some games. Most of the time I don't get very far into them, though. Most recently I've started playing Fire Emblem Engage.
The only other tweak I've made beyond the base OS is to install CryoUtilities (see announcement video
here). It helped me to get Midnight Suns running like a dream despite not being verified.
Speaking of not-verified games, you can check out
ProtonDB to see reviews on how any game plays on the deck and what recommended settings people suggest.