Been using zram since it hit the kernel, with the same priorities "petard" and disk backed swap. I don't remember the details now, but zswap many years ago would not handle hibernation "well" (as well as it can get..), or not better than zram+distinct hibernation with -XXX priority. But zram definitely has some caveats with that setup and it will lead to disk cache being used and requiring manual flushing, for example after hibernation, because zram-generator (if you're using it) isn't ready yet on resume, from what I recall about it. This seems like such a neatly written post I'm going to try and go with zswap from now on.