How to allow access to Posit Connect for external users + (not) restricting their content access

We have an on-prem Posit Connect server running. We have several external organizations that want access to several applications on Posit Connect. What's the best way to set this up? Ideally, these organizations only see the content they're permitted to, so they'd have to be user-authenticated. Likewise, is it also possible to permit access to specific Posit Connect content WITHOUT having a user account within our organization? For instance, board members would like to have access too, without making an account.