what is the best way to do this

Hi, I'm new so I hope I'm not looking like it takes me an hour and a half to watch the TV show 60 minutes.

Here's what I want to do.

I want to have each new person be a free or paid member.

They get their own site that I have templates for with the template plugin if I understand that.

I want to have 1 free and 2 paid levels. All levels can build their site but the paid level get's more functionality and the top level get's more still.
I want them to have the ability to make their own forums, chat etc.

I want to be able to go to a million users if it grows that much.

My questions are:
1. Do I need MU/BuddyPress or just BuddyPress? And please say why? I looked at an old thread here from 2010 https://premium.wpmudev.org/forums/topic/do-i-actually-need-mu-or-just-buddypress

But that's a thousand years in internet time.

2. Would it be best for me to use the Member plugin or pro site plugin to get these levels and payments?

3. How do I control the amount of functionality they get at a certain level? I.E. Free they get a super basic site. OR they get main site access.
Paid level #1 they get a basic site to build. Paid level #2 they get a much expanded site to build.

How do I control that?

4. What's the best set of instructions to do what I need. I saw there was a plugin that looks like it installs MU for me? Not made by you guys, someone else. What's the best way and clearest set of instructions?

5. If I understand. If I don't use MU then my users don't get their own blog. If I use the new WP internal multi user function then they all blog and contribute to the main site? Is that correct?
Do they at least get their own separate sections/areas in the site?

I know I've asked a lot of questions so I really do appreciate your patience.

Thank you, Patrick