The models are created, posed and rendered in DAZ3D. As for a demo length and inclusion of content, I'd say you should try to have at least a half hour worth of content for your first release. If you can sneak in one or two sex scenes in that time, that's also great. Doesn't have to be with the main characters, but you need to have some kind of a hook. If the story is engaging enough though, you might be able to postpone any sexual content and develop it more slowly.
Thanks for the advice, trying to avoid DAZ3D but ill check it out a bit more. Right now I'm using Blender to render the scenes and character models. It is quite difficult I would say lol but its easier to import to Unity as a blender file. I am putting a lot of effort into the story and interactive material within the VN. MC can basically do anything, but mostly sticks to a management system as well as a relationship building system. Iv put a lot of work into the multiple endings and scenarios. Most decisions effect the actual story and can be seen in game as Consequences(Some character will leave, die, or develop different relationships accordingly). The idea is to have a full game with days of content to play with. Super ambitious, but a little more work goes a long way with these VN's. If your interested I'd love to have your opinion on the demo before public release. Still a ways off but it'll be done after I touch up some mechanics and characters.