to update:

My bag did fit in the Ryanair sizer and the Air Baltic sizer (which felt slightly smaller than the Ryanair one...). No issues in WAW or in RIX. Noone checked, noone weighed it, no sizer check, nothing.
Actually I was a bit disappointed they didn't check other people's bags. They were quite lax on the checks. Looked like lots of carry-ons were over the size limit (and judging by the bulging on some the weight).