I use the GPD pocket and its magical when flying to roll up with a laptop on a plane with a 9-inch screen. My model even has an i7 in it so it can handle some games. Only major complaints is that I had some issues getting the screen to play nice with wayland (Ive since fixed it, it was just effort) and its keyboard is an ergonimic train wreck.
Yes, but im already using the computer for other things and it would be more inefficient to double up on heating sources. I can confirm from personal expirence a PC in a small room can sufficently act as climate control.