Hey!
If you want everything related to each creator to be separated, profiles are indeed a great solution! You can have a profile for each one with any social media apps needed installed and configured for the accounts you need.
For app installs, please use Google Play Store, since the social media apps you mentioned are proprietary and only officially distributed through there. Anything else can become a security issue. It's your choice if you want to install and push apps from the owner profile or if you want to do it separately in each profile. Since each profile will need Google Play Services anyway, I'd recommend doing it separately.
Keep in mind that Twitter (X) doesn't allow signing in on GrapheneOS. You'll have to use the website.
I'm not sure what you need a VPN for. Do you just want to appear to be in the US? You don't need to take any extra steps when installing apps then. If you're doing it for privacy or so that the accounts appear unrelated to each other, I guess you could use one, just make sure to rotate IPs. You'll have to install a VPN app in every profile.
I hope that helps!