No, Halion 5 is completely replaced by Halion 6 so there’s no point in removing anything, the installer already does that anyway.
Nearly all of the Halion Sonic SE content is exclusive to Cubase users and isn’t included with Halion 6 or Halion Sonic 3. Since this is barely over 1GB, there’s not much point in uninstalling it.
The full version of Halion Sonic 3 doesn’t replace Halion Sonic SE in your projects.