Thanks a lot, yeah I would go with pixelOS as well I think. What do you mean "using a aawireless device"?Im not 100% sure the procedure for unlocking the POCO but for my redmi note 10 pro..
1) Unlocked the bootloader using the miui unlock tool
2) You can flash miui back and return to stock if needed
3) Banking apps, NFC all works but this depends on the custom rom your installing.. Im using PixelOS
4) No cons for me at all, everything works such much better on the custom rom but again it depends on your device and which custom rom you install.
As for the android auto wireless issue its well documented in various forums, and is the same if your using a aawireless device. They just dont want to address the issue in miui and this is why
its been broken for so long.