I'm a windows man, most of the public uses windows i'd say, some use mac but not as many as you'd think, they just tend to be more visible due to compatibility and things, not that that is bad in fact Mac is great for some stuff. Ideally you'd want a mac version too but if it's your first time i'd play safe and stick to windows. Linux is great but niche, they also tend to be able to emulate their way out of a hole, they may be able to play the windows versions anyway.
as for engine for a newbie go for Ren'py or twine, both relatively easy to pick up, though it can limit your options of game type a little, at least for beginners anyway.
Game type, i'd advise against either a hard sandbox or purely linear VN and here's why, if you go hard down either route you'll need to do it really well, understand exactly what each type needs well in advance and crucially also know what doesn't work for that type of game. VN's can build characters easier, they are dialogue heavy and benefit from more screen time per character, this means that large casts don't get the time they need, meaning your narrative won't feel important and could easily become skit like and shallow. the opposite is true of sandboxes, large casts that you can choose to interact with or not without a structured story gives you freedom to do whatever you want in whatever order, though of course telling a story in this way would be very tough.
In short Pick a type but don't exclude ideas from the other type, go for a less linear VN or a sandbox with an overarcing story, this gives you wiggle room, which first time round is important. However if you feel particularly confident in your coding or storytelling go for the format that supports your strengths best, better to play to your strengths first time round and build from that.
2D or 3D is entirely up to you, 2D suggests drawn, this is hard if you aren't the artist. 3D suggests live moving models like in mainstream games, this would be awesome but is most likely beyond the scope of what most beginners can do think though. 3DGC like Daz however is far more accessible and not that hard to get into, I've hobbied a little myself with no previous experience and when i set my mind to it i can get some fairly good results, DAZ is free, the additional materials and assets are charged for though there are places you can go to, minimise expenditure shall we say.
Fetish advice
Suggestions+things i'd like to see done well
The very short version is go with what you like and are comfortable with, better to do something your into than something you're not keen on because it helps the work ethic, i couldn't make a bestiality game, not my thing, i would get board and leave it before i finished.
Don't be overambitious on your first game,don't make the cast too big, keep it small and interesting, something of the size of a night with X, nothing too big, that way if you feel you've chosen the wrong format or piece of software you're not stuck with it for too long and can switch after the initial project rather than pissing off you're audience and abandoning a project for something else.
That was far larger than i first expected it to be, anyway that about covers it.
