Citizens only, and anywhere in the world. If you're not a citizen but are a resident, you can support in another way - go to your friends who are EU citizens and ask them to sign! Even if they're not gamers, remember that it's about ownership in general. There are many other things that can and are being remotely shut down, such as cars, trains, implants for disabled people, etc. This is just the first step in regaining ownership of things you buy. Try asking a few people for support!
No need to show a cookie banner if you are not placing cookies or trackers.
But now that AB 2426 has become law, it moves more in line towards GDPR in terms of transparency. E.g. you have to be transparent of using licenses etc.
What I really like about this new law is that it makes (or should make) it easier to unsubscribe. Just Google how difficult it is to unsubscribe several major SaaS players, like e.g. Semrush on SEO. Good luck being compliant to AB 2426 with that 6-10 step!
Btw, I'm not sure you should show a cookie banner if you're not tracking people. But you must be more knowledgeable than me.