I don't think hot glue would hold for long , some use dowels , marine epoxy , even crazy glue gel ,
I do agree with gluing rocks together it adds that extra insurance policy , it also gives that extra security of preventing any rocks from breaking the glass ,
I never glue my rocks together and never had any kind of problems , the only thing I do is weave rocks so they lock together , don't think rocks are as secure but that's my preference
I do believe over time macros will bond around rock along with corals ,
I would think plants and vines in a freshwater tank would do the same.
Fish are like lifesavers
They come in different colors