Limitations are on the website - https://grapheneos.org/articles/
I don't care about google pay/wallet or android auto. My credit union's app does work fine, but even if it didn't, I'd still use GOS. It's great.
These days I just care so much about "things should just work" that I cannot justify doing this. I cannot think about how I could spend time figuring out what to do when the repo is no longer maintained or something breaks for random reasons.
and if you did you could use curve pay instead. Basically the same thing with more features, the only catch is that they charge FX fees after surpassing a limit (but that can be mitigated by paying with the same currency of your linked card, thus never executing a change in the first place)