If I understand correctly what you want to do, this should work: set the default left-drag action in *both* contexts, MIDI CC lane and MIDI CC event, to the same action, "Draw/edit CC events ignoring selection". (You can also set shift+leftdrag in both contexts to "Draw/edit CC events ignoring snap and selection" to draw smooth curves without snapping to grid.)Any action initiated in the event rectangle is handled by the "cc event edit" context/settings. To get the actual "ignore selection" from the cc lane context, you have to click outside of a selected event.
You can't have a draw tool (like in envelope lane) which overwrites anything underneath it, regardless of selection, and that exact thing is causing much friction.