Do you have any guide on how much better you are without soldermask? I was imagining some bigger areas to be soldermask free, and having smaller 'islands' covered by it.. but as we don't know how the ground plane looks like it's hard to say.

You can set the layer you want to affect with your zone after you activated the zone tool. There will be a different dialog pop up that gives you some options.

What you do is that you are doing one zone on either F. or B.Cu layer and you create another zone on the F. or B .Mask layer?

Appreciate your sharing.Please keep up your updates.