Hi, I'm from Finland and while I can't directly help with the aspects you mentioned I have a side of this coin you might want to consider adding to the tutorial if it ever comes to life.
The mention of my home country is relevant here because our government is simplifying parts of our taxing process during the two weeks from December to January. This has come to mean that some places simply won't process our VAT id's as our government database is not in a state to confirm them. This has lead to me being unable to re-new my monthly Megascans.se subscription, and now I'm barred from A) using the Megascan Studio to work with the assets I've paid for and B) use the extra money I've deposited to their system. The money stands there as credits but I cannot spend them because my VAT id cannot be validated. That's basically them holding my money as random until I pay more money as subsrciption fees and now as deadlines near it has grown to something incredibly idiotic that I'm now trying to communicate to my clients because now I need to resort to Photoshop and such instead of getting certain snow shaders done in the Studio. Since I have a freelancer subscription there is no paying through Paypal or any other method since the VAT problem is still there.
Mind you, I had trouble with this just two months ago because of how I needed the monthly fee at a certain bank acccount but had to await for my bank to get its shit together so I basically warned them this would bring trouble and begged Quixel to reconsider their payment system so I could at least edit the assets I've paid for but they didn't see an issue here since Shutterstock and some other examples they managed to dug up also use a system where you cannot keep your account in "passive" mode if nothing worth paying for appears for a month or two so - and correct me if I'm wrong and something changes, but that last time they basically they said if I won't keep the account active by paying every single month even if nothing new or interesting shows up the accound will be wiped so say goodbye to your stored payment info and a chance to re-download your paid models in case of a hdd breakdown I guess. "Want to download that one rock with the extra money you've deposited for a rainy day? F*uck you, to use that money of yours you'll need to pay us more money. Yes, even if we have nothing of worth to offer you this month."
Perhaps the funniest part is I can click on an asset I don't have but would very much need right now and there's a text there saying "You have 38 points Get more!" reminding me of the extra points I've paid for. And then where there should be a button allowing me to spend said credit, a button called "Download" there's now a button called "Subscribe now" so nope, no downloads for me but yeah - I sure are hell am allowed to top up my account even more!
I'm very glad Designconnected, 3DSKY, CG-Source and Textures.com, to name a few do not practice this system.
Anyway, since you're doing your best explaining the workflow between the two, maybe be sure to mention this as it has kind of a crippling effect to the superb system some mastermind over at Quixel has come up with! Might save others the trouble of subscribing. Now as days go by and the VAT validation still won't work I'm waiting for the moment my account with all the bought assets gets wiped. Good times!
EDIT: After writing this, this morning, my payment finally went through so hooray I guess altough that's one deadline and one pissed off client that this won't fix. I hope Quixel gets their act together or I'm done with this shit. Thanks.