Hi DaemosChronicle,
for 2. you need to confirm the tree at the top first. I agree that it is a bit weird that you have to do this with only one tree, but once you did it you should be able to click on the nodes below.
Regarding 1. there are a few plugin settings that you can use to make the nodes smaller. Here are the relevant settings: https://imgur.com/a1zCUVN
I suggest lowering the width and height a bit and maybe even make the gap smaller. You can also change the font sizes in the plugin settings.
Best regards,
Felski