GrapheneOS is the way to go imo. Calyx is a good alternative if you don't have a Pixel (especially when compared to other privacy OS or so called "privacy phones" - avoid those), but a few searches comparing the two should yield the reasoning.

Some GrapheneOS staff are a bit intense in defending the OS against myths and when measured up against CalyxOS. Might turn off some people, but putting that aside, they aren't necessarily wrong.