A good thing to do here is frame it as an introduction rather than a referral.

For your friends who you think may be a good fit generally, get their resume and give it to the relevant hiring manager. Tell the hiring manager you know them well, and their good characteristics, but make it clear you haven't worked with them and so can't vouch for their hard skills. Suggest it may be worth an interview, then leave the decision to them.

For your friends who you don't think will be a good fit, that's obviously awkward and you'll know best how to deal with that with each individual concerned. But the line to never cross is the the honesty one - if you honestly don't think it's even worth an interview, then don't tell the hiring manager that.

A good thing to do here is frame it as an introduction rather than a referral.

For your friends who you think may be a good fit generally, get their resume and give it to the relevant hiring manager. Tell the hiring manager you know them well, and their good characteristics, but make it clear you haven't worked with them and so can't vouch for their hard skills. Suggest it may be worth an interview, then leave the decision to them.

For your friends who you don't think will be a good fit, that's obviously awkward and you'll know best how to deal with that with each individual concerned. But the line to never cross is the honesty one - if you honestly don't think it's even worth an interview, then don't tell the hiring manager that.