I organise photos in filesystem directories. I want the ability to preview one photo in a big frame and to preview many photos in grids. I want basic filesystem copy rename move delete operations for directories and photos and other file types.
as far as i know gThumb accomplishes all your requirements and even more like easy editing, printing, deduplication and some further features via extensions.
pix is the "platform-independent" fork of gThumb 3.2.8, which will suit your environment better if don't use GNOME3.
maybe also Geeqie as a even more lightweight alternative is worth a look.
What about digiKam? I am using that now for a couple of years and it works quite well. Have a look at digiKam.org