The Steam Deck only has a single USB-C port on it, so you would need the dock for USB-A ports. The good news is that the existing USB-C port is on the top of the Deck and the dock connects via a short cable. You can use the dock as a stand but it’s not required.
I heard from a “friend” that it runs very well on a Switch emulator on a Steam Deck. Some pre-rendered cutscenes are janky. It has a pretty cool system where you can take a screenshot that will pin to the map to indicate places you need to find back to once you unlock a new ability, and sometimes those don’t render right either. But otherwise, gameplay is flawless. Or so I’ve heard.
I’m replaying the Arkham series and I’d forgotten that Ashley’s VA plays Oracle. I couldn’t figure out why I was getting annoyed every time she called Batman until I made that connection.