My guess it is will be much, much closer to classic Trek storytelling than ANYONE here is expecting.
Tarantino has a sometimes very crude humor, loves violence, and stretches single scenes to inteeeense lengths. He won't do ANY of that in a franchise film! (It helps he isn't directing it as well)
Whatever Tarantino cooks up - it will be the basic plot behind it. It will be a much more streamlined, mainstream movie than, say, "True Romance" was. Basically, it's Tarantino's way of not doing a Tarantino movie. Something he already wanted to do when he wanted to do a Bond movie - but he never had the chance to do it, and he can't do it with one of his own "regular" movies or he risks diluting his own brand.
I say, the Tarantino project is one of the most exciting things (right after "Picard"). Because Tarantino is a really smart guy. And this would be his movie where he lays down his signature style, and all there is would be purely Tarantino high-concept, but without all the superficial "Tarantino"-stuff.