Author of mergerfs here.
As I understand the unionfs plugin supported multiple technologies but now only mergerfs. Perhaps it's just a documentation problem but I seem to notice a pretty high rate of questions in the vain of "How is the UnionFS plugin and mergerfs different?" or asking about the plugin in ways that implies the person doesn't know that mergerfs is ultimately being used which I suspect makes it harder to find information about mergerfs.
So I'm wondering if it'd be worth renaming the plugin to "mergerfs" or "unionfs (mergerfs)" or somehow make it clearer what's the relationship and where info can be found.
I don't use OMV (and therefore the plugin) so I might be missing something but from the outside there does seem to be some confusion.