I hear from more and more people that they are going new ways with their phones in terms of privacy. The new and I think better way is to split your identities with 2 different physical devices. One is your real life phone and the other one is your privacy phone. You have less stress with running normie apps on your real life phone and a privacy phone with a KYC'd sim card and banking apps on it is also not the best way.

The important thing is, you have to be aware what you are doing, if you have bad OPSEC a phone with GrapheneOS can't help you. You have to identify your threat model which is some work but it's important to work on it to reach your goals. Also important to know is that everyone has a different threat model, copy pasta something because some other guy said so is wrong and can bring you into troubles.

Best privacy OS for your privacy phone is GrapheneOS without a doubt.