Harem route is vanilla but they still end up calling the MC master for some reason. Sex is kinkier in whore/slave route. Whore/slave route are differentiated by whether you have prostitution on or not. Frankly, harem route felt boring to me and like what was going on never really matched the way people were talking. It seems very much like the game is built around the whore/slave route and then a vanilla option is added on afterward, even though I know from the development cycle that it's actually not the case.
You probably want to play the slave route. It's kinkier but without any prostitution or group sex apart from ffm threesomes.