Yep I read about that when I first looked into exwm and it is a problem. I'm lucky though, I only really use emacs and firefox so it's not a big deal for me. I wouldn't want to be using exwm if I was doing some serious multitasking and using video editing software or something. I don't know if there are plans for a multithread rewrite of emacs but I hope it happens.
I'm going to set up lem.el at some point! I currently use elfeed to see lemmy posts from the communities I'm most interested in and firefox to comment or just browse about. I actually saw this post from inside elfeed originally.
Not always, I have one with an amd chipset that I can't get Linux on (last time I checked).
You have to open them up and remove a screw then install different firmware.
The dell Chromebook 11 I got from eBay for under £20 was easy to get it working on though.