Consumer routers should be default deny so if you don't add any rules you're safe.
My IoT network has a very controlled list of allowed outbound targets in the ipv4 world. If I blindly enabled IPv6 I’d have to ensure I protected against that too.
Of course I also do things like intercept UDP/53 and nat it to my pihole as some devices have hardcoded dns servers, which many purists claim is an “ugly hack”.