When freezing arancini, would you suggest doing so before or after frying in oil?

I disagree. I have frozen them before (un-fried), then thawed them overnight in the fridge the day before frying.
-Put them on a sheet pan, freeze till solid, then bag 'em.
-Back on the sheet pan the day before cooking, in the fridge overnight to thaw.
-Fry.
Frying them before would make the breading gummy, especially microwaving them from a frozen state - too much moisture.

Definitely after. Then microwave them back to life. They won't be as good as they would be straight from the fryer but if you need to hold on to them that would be the best way.