Steam Deck

You like playing games in a handheld style.
1. With the steam deck, the console is the controller.
You have a decently built up steam library. Indie titles work particularly well.
1. Note: If you want to build up your steam library, check out https://gg.deals/.
You're interested in emulation (can do up to certain xbox360 / PS3 Games)
(Bonus) You have an interest in tinkering with computers. In this case Linux.
1. If you don't want to tinker, you can stay within the console-esque path and not really dive into the Linux stuff, but I find it hecka fun to do so.

You want to play AAA games for hours on end away from an outlet.
You only like playing with keyboard + mouse as opposed to a controller.
You'll depend on the steam deck as a dedicated desktop / workstation.
1. While it does work for this with a dock, a monitor, a keyboard+mouse; you're sort of just reinventing the laptop. Also the built-in OS doesn't lend itself that well to a fully hackable Arch / Pacman experience due to its immutable filesystem.
  tldr: if you want to play video games, get the deck. If instead you want a workstation, get a laptop.
You mainly want to use it for windows.
1. Installing windows on steam deck seems like a bad idea to me, though I've never tried it. You'd be better of with an actual windows handheld.
You want high resolution + high refresh rate.
1. Steam deck's built in screen is 800p@60hz. This is a fine level of clarity for the small screen size and it performs well in terms of FPS / power efficency. If you use an external monitor, 1080p@30-40 is often possible, but anything beyond that is likely out of reach except for the most basic of titles. OLED model has an 800p 90hz screen.