Haven't used Ditto before but I use CopyQ on Linux, at least according to the screenshots of Ditto it appears that CopyQ has been influenced by it

Maccy on MacOS is perfect: https://maccy.app/

I use maccy on my wife’s Mac and don’t love it, maybe it’s bec I’m still not comfortable with Mac keyboard shortcuts or maybe it’s just the UI, but there’s something about it that feels less baked than ditto.

I don’t know ditto but on maccy it’s just the paste shortcut (for the last copy) plus a number (if you need an older copy). Could it be easier?

A way to sort of "alt-tab" between copy versions instead of separate keypresses for each?

I don't understand what you mean. Sorting: There is no shortcut for sorting. However, I have never needed this either, because the search via regular expressions Fuzzy or a mixture of both works very well.