Frieza is weaker than Goku's weakest iteration of SS. 19 and 20 are weaker than Piccolo and Vegeta (who are both stronger than the Goku that fought Frieza) but still noted to be beyond any of the other post-training Z Warriors. I really don't see how you can reach the conclusion that Frieza is most likely stronger than 19 and 20.
he might be stronger than the other weaker androids from this movie, but he should be weaker than 13.
14 and 15 are strong enough to force post-Android training Trunks and Vegeta to go SS, and 15 was able to knock SS Vegeta back down to base. That's way above Frieza's paygrade.
DBS Frieza, sure. But not DBZ Frieza, which is the iteration this thread is about.