Sync ~/.gnupg dir between multiple Macs? (GnuPG / MacGPG)
Yes, it is certainly possible. The files in ~/.gnupg are just ordinary text files - there's nothing that "binds" them to one specific machine as such.
You can do it either by adding the files to an already-synced folder, and then linking them into ~/.gnupg - or by choosing ~/.gnupg as the folder where you want data synced to (you can choose that individually for each folder that you sync from Resilio).