I lived in a totalitarian regime similar to the ones you mentioned (Ceausescu’s Romania back in the ‘80s) and if his bad guys had had access to today’s surveillance tools we would have been really, really stuffed.
As things were you “only” had to watch out for people who would rat you out to Securitate or to Stasi (in East Germany), not an ideal situation but manageable from a certain point on, one could live a decent life from a “freedom” point of view, to say so, you could say political jokes or complain about the regime to the right people, i.e. not the regime’s informers, or you could directly “steal” from the State things you believe should have belonged to you, like the peasants from my grandma’s village were doing when they were taking stuff at night from the State farms that had been built on lands nationalized by the State from the same farmers immediately after the Communists came to power. All these things were highly illegal, I mean the regime trash-talking, the taking of stuff from State farms, the only thing protecting us was that the regime couldn’t follow us all in order to catch us. With today’s tools that would not have been a problem, you can see that in today’s China where every form of political jokes (even in private online conversations) is prohibited and actively acted against.