I don't think you should conflate those two things. I've run GSuite for a number of vanity domains since they started offering it way back when and have always

I don't think you should conflate those two things. I've run GSuite for a number of vanity domains since they started offering it way back when and have always had my actual Google account tied to my OG Gmail ([name]@gmail.com). In this way I don't have to worry about dealing with a split-horizon type situation if I ever decide to pull those vanity domains down and move them elsewhere. That and I don't trust Google to not do something evil (intentional or otherwise). I don't want to be in a situation where I'm locked out of things I paid for or payment accounts AND be locked out of the vanity domain(s) email. The other nice side effect is I only use my gmail.com address for Google account related things. I don't get personal email there anymore and that inbox is pristine which is impressive since I've had it since Gmail launched. My GSuite account, on the other hand, is quite a dumpster fire from years of personal email, aliases, and adding in other domains from time to time. Part of me would just like to walk away from it but too many things are tied to a number of email addresses in those domains. I really do prefer Fastmail at this point, but I don't want to move these particular domains given how much junk gets sent to those addresses. But... I wouldn't suggest using a vanity address as a primary Google account. Managing the two is worth the overhead and risk avoidance.