The primary privacy protection a VPN provides aside from masking your IP is it stops the network you're on from knowing what sites you visit (free wifi, etc.) as well as your ISP from knowing what site you visit. Your traffic will be encrypted via HTTPS regardless of if you use a VPN so the only damning information without one will be that you visit kiwifarms.net through your DNS requests. Personally I would reccomend using a VPN if you're connecting to Kiwifarms from a public/untrusted network or you live in a speech hostile nation (UK, Germany, Australia, etc.) but even then chances are they probably won't look into you personally without suspecting you of a crime first.
Unique password, username and email are definitely higher up on...