As a previous Pixel owner(P4XL), I find it odd that so many people using them, are running graphene. Granted, I ran it for quite some time, but that was after Google gave me the finger, in regards to support.
IMHO, I found the cons far outweighed the pros. The biggest con, obviously, is losing proprietary features. As far as security goes, if there isn’t an Android device that satisfies your needs, out of the box, then maybe it’s time to look elsewhere…😇