In my opinion, you're off on one thing: NTS fits better for building a cuckold fetish where the protagonist is a beta, since he's consenting to it. The whole charm of NTR is that the protagonist stays completely in the dark—Netorare is all about that mystery and intrigue, while Netorase is about acceptance and actively participating, whether in an active or passive role (that's how I see it anyway).
As for making the protagonist a weaker beta type—yeah, there's definitely room for that in my game on the NTS path, BUT there's also plenty of space for a protagonist who wants to take charge in exploring his own sexuality with other girls, rather than just being Mia's submissive sidekick on her sexual adventure with people and monsters.
I've mentioned this before, but the game is planned to be huge, with tons of branching paths and different fetishes. In the end, it all comes down to the player—what they steer the protagonist toward is the content they'll get.
The problem is what is defined as NTR & NTS differ per person, for NTR you say mystery & intrigue, I say cheating and loss, is there really mystery and intrigue on the NTR path in this game? The MC is magically neutered, but in full possession of his mental faculties unless you did the exact same thing as virtually every other NTR games and basically gave him a single digit Wisdom attribute, he'll be aware of Mia is fucking around, their is no mystery or intrigue there, he is losing her to others and she is cheating on him, he knows it, we know it.
I know many fanatics of NTR love to poetically say its about 'mystery & intrigue' except virtually no NTR game has truly those because most of said fans gets off seeing the LI getting fucked by others, typically while the insanely oblivious MC doesn't figure it out, again not a single drop of mystery & intrigue there. Ironically if the story wasn't a porn story the NTR would work better in your optic, because the writer wouldn't feel the need to show off the LI getting fucked by others constantly, so they'd actually be having a better time of actually making a mystery & intrigue out of it, but in 99% of the games on this site? Forget about it, NTR is all about getting cucked and losing the LI to the competition, because its the only aspects that work with porn.
So obviously every NTR stories are going to be pretty much about some pathethic excuse for a man getting cheated on, how many of them suffer from the 'small dick' syndrome? Most again. So tell me what that type of character are? Beta Cucks. If you want actually someone that is more along the lines of an Alpha Cuck its typically in the NTS / Swinging & Sharing games, where the MC actually get its fair share of sex, sure you have some of those games with the MC that give away his gf or wife to others and doesn't get any in trade, so their are plenty of Beta Cuck NTS stories here too, but NTR stories in the games here are virtually all about weak submissive males that get their gf or wives taken away, unless its a FMC in which case she get corrupted behind her oblivious husband's back, because somehow when its a NTR game with a FMC instead of having the rare narrative of the bf or husband getting stolen, she is still the one getting stolen.
I mean one of the few games I heard had actually any form of 'mystery' is Wedding Roaming but again if you play the actual NTR path you are aware of the fiance cheating because you get to see pictures of it, its not mysterious at all, and ironically the 'Love Path' where nothing happen but which use most of the same content as the NTR path without the pictures that do show cheating, is actually the closest to actually be fitting your description, except in this case its because nothing actually happen, it just look constantly like your fiance and supposedly best friend are perpetually getting way too close for comfort.
I did pay attention to the story and the elf took him back then he had a choice to wait or tell her to fuck off. Telling her to fuck off is what an alpha cuck would do(to use you words), but when he agreed to wait in the other room for her that is what a cuck would do which means even though he wasn't happy he was willing to listen to her and his decision to leave or stay will slightly affect the NTS story going forward I believe at least that is what Skinny Rat said.
I don't understand what you are talking about.. the MC had originally a gf which cheated on him and left, he was by no mean happy or in support of that, after which he died, and was reborn in a fantasy world, now you talk about an elf? What elf? The cook that tells the MC he should share his gf? Just because he listen to what the guy say doesn't make him a cuck, just mean he isn't a hothead. Or do you mean the elf girl the MC can fuck in the woods? If he chose to fuck her its not really NTS since she isn't his gf or wife, he merely is fucking her. As for what it mean for the narrative its painfully obvious, the Dev is trying to teach the MC a lesson, on the NTR path I suppose its either let it happen or lose her, on the NTS path I suppose its going to be more along the lines of if you both let yourselves loose it will be better. Or effectively its a message to the players, 'you better learn quickly to let go otherwise you'll get pretty sore with this story because their is no keeping your gf all to yourself'.