Removing padding from gallery blocks

I have a site for photography which uses mostly gallery and image blocks.

1) When using an image block I can adjust the section height so that there is very little padding above or below the image. However, when using gallery blocks there is no way to adjust the padding above and below the images and there is currently more than I would like as all the different sections are now quite far apart. 

Is the best solution to only add images as image blocks or is there some custom css I can insert?

2) I currently have images in columns of 3 but may have to change it to 2 so that the image groupings work for desktop and mobile. When I change it to 2, the images are much larger than I would like them to be. Is there a way to change the size of the image boxes, aside from just increasing the padding between them?

#1. I think CSS can fix this. If you share link to page where you added gallery. We can check easier

#2. Which page url?