Pricing Tables, Payments, and User Upgrades... How do they work?

Hi,

I'm starting to look at paid membership options, and I'm just hoping for some clarity.

I see that Xenforo has something called "User Upgrades" and there are also several add-ons for " " @Ozzy47 and " " @XenConcept and maybe others too.

And of course there are payment systems, like PayPal for example.

Bu my question is, how do they work together, or do they not?

Is this the correct flow:

1. Set up payment system (Paypal)...