I think to go off topic is frowned on and the site admin prefers people start separate topics as in this case. Just a friendly reminder.
I have another post asking specifically about posting through the back-end so Wp User Frontend Plugin won't work for me. But thanks anyways.
I won't list all my plugins but the ones that pertain to managing multiple sites, well I am testing MainWP and ManageWP. MainWP is a plugin you install on each site. The main site has the MainWP plugins, and all others have the ChildWP plugin. They also have extensions which I find useful, such as Clone, then there's another plugin for managing all the settings across WordFence (if you have WordFence installed across all your sites for example).
As far as WPMUDEV, yes I've also read plenty of negative reviews. I think their plugin lack solid documentation and they are shooting themselves in the foot. If they had better documentation it would be a lot smoother to work with their plugins. Some plugins have a feature that doesn't work for example and I found a small bug and emailed them about it.
That being said they seem to respond to forum support topics. From my experience, you will have to write a lot and there will be much back-and-forth to ask how certain things work, or to troubleshoot errors. The more complex your project is the more you will have to go through this back-and-forth.
On a side note Restrict Content Pro plugin does have a way to accept payments and then create a new sub-site on WP multisite installation. It's an extra extension to their plugin and it's on their site.