As long as it's not an ARM Chromebook, yes. (I think due to ARM just being difficult to work with in general rather than malicious behavior from Google?)
Also note that you'll most likely have to open it up and unscrew the firmware protection screw. It's kind of annoying but it's not difficult and at least it's not iPhone-style "impossible".
Yes. The ARM Chromebooks suffer from long term support issues just like phones. Qualcomm and the other chip vendors will only support a given chip for a few years, and then that's it.
For x86-64, the peripherals are mostly standard, with the sometimes exception of suspend / resume support. So a regular Linux distro will often just work with little tweaking required.
Also note that you'll most likely have to open it up and unscrew the firmware protection screw. It's kind of annoying but it's not difficult and at least it's not iPhone-style "impossible".