1. There's a global gallery that I can add individual albums to 2. I can create dedicated shares, starting with the content of one album then add other pictures from other albums
There's no way to create additional gallery-like shares that contain multiple albums in the same style as the global gallery. One really obvious use-case for this would be to share an entire folder of albums (e.g. a folder corresponding to a music festival, with albums for each band).
I can create one uber-share with all the pictures in a folder. But it's tedious work and loses the album structure that I'd much rather keep!