Is a Chinese phone's stock OS better than GrapheneOS for my threat model?

Get two phones. First Huawei or any other one Second Google Pixel 7a or newer with GOS. If the LE pulls you over you show them your innocent Huawai phone. The GOS phone is hidden somewhere. As long as they not suspect that you have a second phone somewhere you are good. If they search for the second phone you are pretty much f*cked. So make sure that the innocent phone looks convincing and make sure to hide the GOS phone where they will not find it easily.