You can remove it. There is actually an “IoT Enterprise LTSC” edition that is fresh from the start, though it may not support the very latest hardware so install 11 Pro then use Revo uninstaller’s Windows apps tab to remove the junk.

I wouldn’t recommend it. Just install ExplorerPatcher to get the old UI back.

The amount of telemetry is essentially the same and most of it can be turned off in the settings.

Go to your Google account settings and make sure that web & app activity, location history and ad personalisation are turned off.

Then uninstall/disable the Google apps you won’t need then replace them with alternatives from F-droid (add the Izzyondroid repo too) like Cromite (in FFUpdater), Comaps, Thunderbird and QUIK SMS.

You should also follow standard practices like setting a non-easy to guess PIN code and also installing security updates.

Just don’t connect it to the internet. The radio and Bluetooth do not need an internet connection to work and you can use your phone for maps and music streaming.