Do I need to sign in to a Creta account?

To browse, no. To connect a wallet, yes — the connect button will ask you to sign in first, and says so.

The reason is that your account stores which wallet address you connected, so the rest of Creta knows which address is yours. One Creta account works across every Creta app, so if you already have one from the games, clubs or the website, use that.