problem and wishes

5. If thumbnails of different proportions that you all thumbnails were the same height, not width! Even better if it in media library – all thumbnails the same square (?) size, regardless of the size and proportions of the image

Have you check out the plugin options?

Rebuilding your thumbs will fix size issues.

There are some limitations using the the built in gallery system.

I did not resize. By default, thumbs size is 150 x 150. and in the plugin I put the same size. But thumbs not be equal in size to images of different sizes.
https://selftrips.ru/2015/08/14/21876

Did you rebuild all thumbs? Use https://www.ads-software.com/plugins/ajax-thumbnail-rebuild/