Only NTR that's good with Harem is Netori. Already very bad, our friend is ogling mc's mom. NTR/S and harem don't go together
Yes, I agree with that haha, in this case the game will have netorare and surely sharing with the Mc's friend you know to fill the BBC trope, when starting the game there is a warning about the content, but the funny thing is that if you decide to avoid that content you will be missing part of the story, I don't know what the dev means by that, if the player misses important parts of the story in general or what.
If you disable that content, all choices that lead to NTR routes of the story will be locked. They are alternate version of events. Choices have an impact on the story, the story is not linear so there are different events and endings for each route. If a player does not want to follow a NTR route, he can do so. Harem is planned to be one of the endings of the game, so there will be more NTR content than harem.