Yes, for continuity I will also reply here.

I did not mean running SD swap with lower priority (would make no sense).
Your conf is OK. But using compcache caused lots of huge lags/freezes/reboots, so I do not use it at all anymore.

Usage of eMMC swap is due to startup usage, depending on how you start it (as early as possible with hacked rcS-late? or just as I do with an own event.d job?).
My ususal usage of eMMC is like that
around 3-5 MB, but not increasing (else I do a swap refreshing of course).

What do you mean by "move data between swaps"?
A moving of data is not done:
Swaps with same priority are used on kernels decision (afaik), swap with higher priority is used, as long as not filled up completely, Second swap with lower priority will only be used, if first one floods over.
Maybe you mean a "refesh" to clean up one swap (defragmentation) as soon as data usage reaches swap size. Then you may enable second swap, disable first swap (all data is "moved"). And then ("maybe", as not obligatory) disable second swap again.