I didn't check, but I'm sure them sort of numbers are quoted on wiki here and there (not perfect I know). There's also anecdote. Both my paternal grandparents, a couple of aunts, some cousins and quite a it of extended family died in the gulag (or before they had a chance to get there). Only two survived to tell the tale.
The ethnic cleansing of Poles and Jews, if not written down on paper seemed pretty much like OUN- B policy in order to create a Ukrainian state and was carried out enthusiastically.
I tend to believe this enthusiastic ethnic cleansing was driven, not just by fascistic nationalism, but also from the class and ethnic structure of pre-war Poland. Ethnic Ukrainians under the Polish state tended to be the poorer peasants. Their landlords were invariably Polish. This is not to excuse any of their actions.
There was also the UPA directive to get as many of their members into the German Auxiliary Police as possible, in order to get access to weapons and it was that same auxiliary police that were responsible for some of the worst aspects of the Holocaust. Eventually when the Nazis were on the back foot large sections mutinied and went over to the UPA and would have brought a hell of a lot of war criminals with them.
A couple of useful books are E. Bjorkman et al. - Ukraine's Claim to Freedom. Published in 1915, it looks quite a bit at the class nature of the Polish occupation and is mostly written from a Russian/Ukrainian Social Democratic Labour Party/ Social Revolutionary perspective.
Less so would be John Anderson's - Ukrainian Nationalism 1939-45, which while going into great detail of the OUN/UPAs history, really doesn't say much about the big fucking elephant in their room.
ETA - yeah, in terms of numbers scroll down to "Spring 1945-Late 1946" and beyond for figures relating to Soviet repression up to the early 50's
en.wikipedia.org