The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
Hey @Margouillo. Your FAF account works just like your email account: you log into the launcher with an username and a password, and the FAF account is not directly tied to your PC. You'll not need to link your GOG account again, and you can simply reinstall the FAF launcher on your new PC.
