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.
>I don't care about google pay/wallet
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)
FWIW I've tested Android Auto before with sandboxed Google Play, works fine.