I'm not going to be contributing any of my own thoughts to this thread, but I'd love to give RR Buildings a shout out for this type of build. His YT channel might answer a lot of the questions you have. He has several playlists of his different builds, but here are two I think might be a lot of help. He has ongoing releases of his current new shop build (including radiant heat) which might be of interest. Apologies if you're already familiar with his work.

Barndominium - YouTube

RR Shop Build 2.0 - YouTube