I'd get a 2nd phone for that and it never leaves the house/location - living inside a bag with conductive material

Hmm, you should have cheaper and separate phone for work anyway?

It is my cheaper separate phone. Main phone is iPhone which I can test iOS on. Android is mostly for testing, and backup/utility on long trips.

Yes, GOS has excellent compatibility with Google. The play services are sandboxed like a normal app and work great.

Does this mean I could install Google wallet? I feel like this would be the only thing really stopping me.

No, unfortunately.

If you live in the EU then you can use curve pay which can tap to pay.

Why is no tap to pay significant enough to stop you from switching to a phone that is private and secure? You can just carry a card and tap—they're tiny.

Yes you can install and use it (I hold my passes, tickets and loyalty cards in there), BUT payments won't work for now because Google says malware-ridden Oreo handset is safe and secure, but phone without ad delivery network running in the privileged mode isn't.

There are alternatives for payments (scroll the thread, maybe look up on GOS discussion site).

Yes. GrapheneOS maintains 99% app compatibility, and the 1% that is lacking is due to apps using incredibly misguided and nonsensical "antiabuse" mechanisms.

GrapheneOS is often better for testing apps due to it being trivial to test with and without google services, most of the hardening options can be used for debugging and provide a crash log to determine what failed, and there is an easily accessible log viewer available in app info.