The three levels
Viewer can look around, chat with Kevin and comment on actions, but change nothing. Editor is the default and covers day-to-day work: prompts, analyses, content. Manager is for someone who fully runs their own site without needing to be an owner: they get the site-scoped destructive actions but never billing, the member roster or site deletion.
Assigning members to sites, the site-access listing, billing, invitations, roles, site deletion and connector keys stay owner-only. Owners have implicit full access to every site.