pixelfairy In GOS a banking app is isolated even when installed alongside another application. That's the entire point of sandboxed apps.
WhatsApp can only collect data of what you do inside of the app. The most it could do is collect clipboard info (only while in-focus), see what other apps are installed alongside it (but not their activity), browse whatever files you've given it access to (just use storage scopes) and see your contacts (use contact scopes).
I don't see any way WhatsApp is able to obtain any more info from a banking app than it just being installed in the same profile as itself. This would be a massive security and privacy incident if it were possible, and to claim otherwise without evidence is giving people the wrong idea.
If you must use a banking app, make a burner google account, or risk the Aurora store in the main profile.
I would never give the advice to use Aurora store to install a banking app. The Play Store is much more secure for this purpose.
Your enabling and disabling google services as needed. While enabled, google can log time and ip address so keep that in mind.
Use a VPN.
Might want to enable fingerprint for the private profile. You should still need its pin to lock and unlock it, but it will time out, and thats what your fingerprint is for.
You can set a custom time-out for the private profile, including setting it to stay unlocked until device reboot, and put it to rest at any time by tapping the lock icon.