Can the Messaging plugin work on a non-Multisite WP website?

Hi,

I’m planning to implement a site similar to this one: https://www.postscanmail.com/ and I’d like to know if Messaging is the right plugin to allow my clients to log into their own accounts to open their own inbox.

– Is that the best plugin for this purpose?

– Can I implement it on a non-Multisite website?

– Do I need extra plugins such as Membership (I’d rather have a nicer interface than the WP default if there is any other option).

Thank you!

Xavier