Hi ,
Removing the paint will only work for cleaning up edges and cannot completely remove the paint from 1 layer but it can be painted over again. In extreme cases you could delete the layer that needs to be erased and recreate it. This will get rid of everything related to that material however. Also please remember that any paint that was directly applied to the base of the landscape cannot be deleted without deleting the layer, as it becomes the base.
I hope this helps!
Have a nice day,