Put differently: unless the game is purpose built from the start as something that works on a 7 inch screen, I am not sure it would be a good idea to play it on a Steam Deck?
300 hours of gameplay with the only frustration being I have to hit "Steam + X" to manually pop open the text editor from time to time says its possible to even play some decade old games.
99% of the time it's not a problem. When it is a problem you can bind a screen magnifier to a key. I still wouldn't want to play some games on it, games that require extensive typing (duskers is a game about piloting drones through a command line, wouldn't want to play that without a bluetooth keyboard), but for the most part it's fine. Most games, even text heavy ones, have big old fonts and large UI elements.
The games that don't, will show yellow "Playable" rating with a notice that fonts might be small and will need magnification. [2]
Timberborn is a favorite of mine and even with tons going on it's a good experience at 800p. I think the Steamdeck is right around 1050/1050ti performance too and that's better than you'd think at 800p. I'm currently playing Doom 2016 at Ultra and the card can pump 110FPS+ (though I'm limited to 60 on the laptop).
2. While not every game is suitable for the Steam Deck, almost every game that was designed to run well on a gaming console will control well on the steam deck, if it's compatible on a software level.
Honestly, every game that's not certified that I've tried to play, I have been able to craft a control system that feels very nice. The sheer number of buttons helps.
Also, the input mapping is fantastic. It's a little cumbersome but the touchpads work for mouse input and the additional L/R 4 and 5 buttons on the back help.