I have a Steam deck, here’s the answers to my knowledge:

1. Yes, you can connect a keyboard and mouse, and even in SteamOS they let you access KDE in a separate “Desktop mode”

2. Not sure about multiple monitors but you can connect at least one. There are docks made for it to do just that (the USB C cable has display port support I think)

3. It runs a 4 core/8 thread AMD laptop chip so assuming you get a mouse/keyboard it should work pretty well.

4. It has a 5W mode in the power settings in SteamOS so I’m assuming around that much at idle.

5. You can put other distros on it, it’s completely unlocked. You could even put Windows on it if you wanted. I’m not sure how easy the install process is though since I’ve just left SteamOS on mine.

Can you actually use steamdeck as a desktop PC though?

Depends on how many pixels you “need”. Running high resolution monitors, even for basic stuff can get costly performance wise pretty damn quick, but in my opinion that isn’t really asking the same question as whether the Steam Deck can be a good desktop.

You can absolutely use the Steam Deck as a desktop, I frequently use my Steam Deck in desktop mode… using the onboard controls. The only real limitation of the Steam Deck so long as you don’t expect it to be a top of the line gaming pc, is that most people who buy it are never truly going to be able to give anything else other than a mouse and keyboard an honest go, they are too impatient and won’t believe it can work but the sky is the limit for joystick+gyro input (our touchpad + gyro) for computers/gaming.

In short yes. I use it as a mini pc, with dual monitor set-up.