It's not a great user experience currently to onboard someone into the membership. You are basically stuck between the options of using a form and then granting access and making the user go get an email login OR letting them signup directly and join but then waiting for an admin to approve them.

There should be an option to automate this so that a seamless user experience can be created. Could also work to trigger a magic link for the user out of the form to create sign in with a single click.