Pixel phones are basically the gold standard of Android phones for flashing custom ROMs. Google doesn’t lock anything down and provide everything necessary to not only build your own, but it even fully supports relocking the bootloader with your own keys and all the secure boot security features.
In most cases I think Google has an online tool you can run right from the browser to fully reflash the stock OS on it.
The only thing that won’t work is apps using Play Integrity which some bank apps and streaming apps use for DRM, including Google Pay/Wallet. There’s not much you can do about it especially in the longer term, as this is hardware-backed so unless some major exploit gets dropped, you can’t really fake the phone being stock to apps. Reverting to stock should bring back full functionality.
You really have to go out of your way to brick a Pixel and mess with overclocking to do permanent hardware damage.