Flashing the stock Pixel ROM back is just as simple as flashing GrapheneOS, the instructions in GOS website are very good for both.

The only two things I can think of that might be issues are banking apps and Google Pay, if you use that. I use Play services in the main profile and honestly there’s not much difference to the stock ROM in terms of user experience. Even Android Auto works nowadays.

For the banking apps, you can have a look at https://privsec.dev/posts/android/banking-applications-compatibility-with-grapheneos/. Just note that if your bank is not on the list, it doesn’t necessarily mean it wont work.

I’m going to go against the grain a small bit.

The only things I don’t self-host that I use on a daily basis are lemmy instance, password manager (bitwarden), backup storage and a Proton drive box for really sensitive documents.

Email is not that bad to self-host, you just need to pick a reliable provider and hope for clean IPs. Then take care of keeping it secure with standard best practices.

Any VPS provider can access your data via the hypervisor if they want, there’s just no way to prevent it. It has nothing to do with what payment methods are accepted.

If you want to be sure, you need your own hardware on your own premises.