Best option: Pixels, since they are reference designs, and also have support for self-signing builds and using verified boot. You can build AOSP using official

Best option: Pixels, since they are reference designs, and also have support for self-signing builds and using verified boot. You can build AOSP using official documentation. Pricey though. You need to buy the version sold on the google store to get an unlockable bootloader. Carrier versions don't allow it.