Yeah but it was "Cumulative Update for Windows 10 Version 20H2 (19042.508)" not "Feature update"... or both are the same?
RP is mostly after the sign off, not before like in the past. So, official 19042.508 ISOs or ESDs should appear soon now.
You can use it for clean install, only the latest dotnetcu wasn't offered by WU on 19042.xxx. But msft announced 19042.508 will be the final version, so that should be ok soon too.
Not if you have cleaned up, else the uninstall option should be available but there will be new applicable updates soon, so just wait.