Does anyone have an idea of how to do it or even if it’s possible? Because as I am paranoid I would like to close my Mozilla account.
BONUS: How to prevent the installation of new extensions from opening welcome pages because it’s very annoying thank you.
I don’t know how exactly it’s possible. You’d have to figure that out yourself. However, if you use a tool like chezmoi you can most probably sync the correct folders inside your profile.
May I ask what part you’re paranoid about since Firefox Sync is fully encrypted anyway?