In many countries, there are tap-to-pay options permitting using GrapheneOS including Curve Pay and also the standard used by many European banks. US lacks an option but will hopefully get Curve Pay soon. Garmin Pay and Android Pay can be used via a Garmin or Android smart watch so that's what some of our US users do. Pixel Watch works fine paired with GrapheneOS with sandboxed Google Play.

Note installing GrapheneOS doesn't involve rooting. Installing it uses an officially supported process and doesn't void the warranty. It preserves the standard security model and massively improves privacy and security on top of that (https://grapheneos.org/features). It's largely the opposite of most other alternative Android-based operating systems are doing with security.

GrapheneOS != root. You don't have root when running GrapheneOS - it would be a security risk.

Genuinely curious, why do you need root access on your EDC phone? Personally I would stick with a throwaway for experimentation, so I'm curious about your motivation.