I haven’t really used this but the WP-Members plugin looks promising for what you’re trying to accomplish. https://www.ads-software.com/plugins/wp-members/

I found it through a blog post that touches on the same principles you mention and the post might give you more information as well. It’s from 2014 but is still relevant >>
https://www.elegantthemes.com/blog/tips-tricks/how-to-create-a-private-wordpress-blog-and-good-reasons-for-doing-it

I hope this helps.

– Mike