I can answer the second question as I have already opened a ticket on the the question of being able to compress the white space to be able to see more references in a single screen view. Support told me that this “feature” could not be cchanged, but that I could post a suggestion in the user suggestion forum which I have done. They seem very proud of their new User Interface which is very unusable compared to EndNote X9 which I will go back to as soon as I get a couple of papers finished.
In general there seems to be very few ways to affect anything in the user interface. You cannot change screen colors, you cannot customize icons or add back useful shortcut icons that were in X9 but removed in EndNote 20. In general I see EnfNote 20 as a step down.