If you want to approve new registrations, you could protect the content at level 1, for example. Users register free at level 0, then you can review him and change his level to 1 if approved. https://s2member.com/kb-article/how-can-i-manually-approve-user-accounts/
At level 1 you could have the payment button, and the paid content could be at level 2, for example. WP Admin > s2Member > Restriction Options
In the registration, you could have a required custom profile field that requires at least 5 characters, for example, which will keep out most bots that try to register on your site. WP Admin > s2Member > General Options > Registration/Profile Fields & Options
If on registration you don’t allow custom passwords, then the person would get an email with a link to set the password, basically validating the email address. WP Admin > s2Member > General Options > Registration/Profile Fields & Options > Allow Custom Passwords
So you’d be putting the person through several steps that validate and qualify him… Is that more or less what you’re looking for?