Just a quick side note FYI - I've been crowd sourcing banking app reports from users in order to build a (work in progress) list of international banking apps that work on GrapheneOS.
To view the current list and/or submit a banking app report, feel free to check out https://akc3n.org/projects/banking/
Where /e/ shines in terms of easy of use, and Graphene shines in terms of security, Calyx has made wonderful choices in terms of privacy.
"GrapheneOS is focused on substance rather than branding and marketing. It doesn't take the typical approach of piling on a bunch of insecure features depending on the adversaries not knowing about them and regressing actual privacy/security. It's a very technical project building privacy and security into the OS rather than including assorted unhelpful frills or bundling subjective third party apps choices."
GrapheneOS has support for installing the official releases of com.android.vending (Google Play Store), com.google.android.gms (Google Play services), com.google.android.gsf (Google Services Framework) as regular sandboxed apps in a specific profile. These receive no special privileges and the OS itself doesn't use them for anything. They run as unprivileged, sandboxed apps like any others. GrapheneOS simply provides fallback code teaching them how to run without any of the special privileged permissions and SELinux policy they depend on having. Even within the same profile, apps not explicitly choosing to use Google services won't use them because the OS doesn't integrate support for it or use it as the backend for APIs in the OS like the stock OS.
Also, this was tweeted recently explaining the up and coming improvements, how they were made and an insightful look at how the sandboxed play services compatibility layer works.