Photo Library Zoom 15.0.1

I'm not sure what you mean. Thumbnails can be sized from 3 across to 9 across. Previews take the whole screen the right of the Sidebar. In Full Screen mode, the sidebar disappears, so the preview is full screen.

To go through a set of pictures to pick out my favorites, here's what I do: I have a keyword, NotFav, that I set with a shortcut that calls up the keyword in one stroke. I use X. I make a Smart Album like this,

with the album name I'm currently curating. At first it has all the pictures from that album. I go through them and quickly find some that I know won't work, and I hit X on each of those, and watch it disappear from the album. I go back through and X away more pictures, cropping and editing to help compare them. Finally, I'm left with only the ones that are not NotFav, and I mark those as favorites. Then I try to rate those.

I like having a way of removing the ones that I don't want rather than having to choose the one I do want. Actually, I do both.

If I understand you correctly, when in Apple Photos on a Mac and viewing the Library, you can select one or many photos to delete by holding down the Command key and clicking on the photos you want to delete. If they are all contiguously next to each other, you can select the first one by holding down the Shift key, then select the last one, and all photos between will be selected. Once they are all selected, use the Command + Delete keys together to delete them all. They will go in the “Recently Deleted" Photos Trash Can, which will automatically permanently delete them after 29 days, or you can Permanently Delete them by clicking on the "Delete All" button in that "Recently Deleted" folder.