I have been using Oneplus for a while now and I jat changed to graphene. There is one thing on the Oneplus that I believe it could be nice, not only in terms of privacy but also in usability.
It's simple, on my Oneplus when I entered a password it runs the profile attached to that password, and if I block the phone again and enter another password, which was attached to other profile it will automatically change profile.
It's a nice idea, as if at any chance someone forced you to unlock the phone you could choose to boot the profile you want to give access to, for example.