As you mention, in terms of sexuality, there is Wilhelm Reich but, on the one hand, you get the extreme prudishness of the Chinese Communist Party that emphasized pre-marital chastity, prudishness to the nth degree. I am less knowledgeable about sexuality in the former Eastern Bloc, though I suspect it never approached the repressiveness of China.
--- I can only speak about the USSR itself, and that only second-hand, but my impression is that they had a "don't ask, don't tell" about just about everything sexual outside of the traditional married couple, which was supposed to be the foundation of Communism. The first sexual partner of the average Soviet citizen, as far as I can tell, was his or her spouse (people usually got married about the age of 20). If a CPSU member got divorced, for whatever reason, that was the kiss of death -- you would get expelled from your party and your career would be over. (Today, on the other hand, the standard pattern seems to be to get married at 20-23, then get divorced a few years later.)
I suspect one reason for marrying so young was that getting married meant you could fuck.
Of course, there was a lot going on that was never talked about, like homosexuality and prostitution.
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