For Epic Games, I’d also recommend Heroic. You can download it from the Discover Software Center in Desktop Mode.
Some quick tips:
If you need to bring up a keyboard for whatever reason, you can hold the STEAM button, and press X.
Expect to tinker and play around with things, I think the software is still a bit new and rough around the edges.
Search the Discover Software Center for software in general; it’s a good place to download things like browsers and applications.
If you want to know if a game runs or not, you can check www.protondb.com , it’s a crowdsourced version of Valve’s “Steam Deck Verified”, where people say how well games work.
Some game recommendations, based on ones I’ve played. Not had a chance to try them all on the Steam deck, but they should work:
Stardew Valley
Baba is You
Celeste
Cuphead
Dicey Dungeons
Slay the Spire (Think you have to use the touch screen though)