A different scheme awaits

To be honest, it sounds too broad. It sounds like you're smashing a college RP, a highschool RP, a mob RP, a RL adult RP and a horror RP together into one place without really much to connect them except they locale. You really need more opportunities for interaction between various "factions" if you will or members could well be flailing around trying to figure out what they're supposed to even plot.

Narrow your focus and use one of my favorite rules of thumb: form follows function. Okay, so you have Las Vegas. You'll likely need all the casinos, drive-though chapels and adult entertainment that goes with it. That's all 21+ stuff, so in order to really have characters "get the most" out of Vegas, as it were, they'll need to be 21. You'll need owners, workers, entertainers rivals, etc.

If you're going to open it up to the mob, then you need to have that an entrenched part of your plot, with canons. Mob holds in cities don't happen overnight. There's going to be history there. I always like to leave room for members to introduce their own factions, with the understanding that they'll need to grow into a powerhouse IC. (And don't forget the cops!)

None of this is HS stuff. If people want to make a character that age and have plot ideas for them, let them, but don't market yourself as a HS board. Same with college. Sure, you can have college kids involved in this stuff, but it tends to be to a lesser extent. In just about any city, college kids tend to live in pretty different worlds than the rest of the citizens. The University of Las Vegas isn't even in Las Vegas, it's in a neighboring town, well outside of the main "action" of the city.

If you want to make a HS or a college board in Las Vegas, then go that route, but you'll need different IC areas, factions and events to accommodate for those characters and that environment.

1) Both gangs and mobs involve killing and money. Gangs tend to be more territorial on physical areas of the city and some of them actually see themselves as protectors of that area. Some of the biggest RL gangs are highly profitable (at least to the people at the top) "businesses" as it were. As for what you should do, that's your call and what kind of setting you want to play in. But you should give some kind of relationship between your factions. It doesn't have to be full out rivalry, but some basic relationship that other members can use as springboards for plots.

2)Not at all. I'm just saying that focusing on the mob and HS students is pretty hard and you'll leave members floundering trying to figure out how they'd interact. Normal people are fine, after all, people in crime have family and friends that aren't involved. Shop owners sometimes have to play protection money and in a place like Las Vegas, having IC casinos is a must and many of the works and entertainers there are normal, everyday people. If you want to go the college or HS angle, go the college or HS angle. You can probably fit in gangs in either of those pretty easy, but the mob no so much. With everything you listed in your first post, it could be difficult for various characters to interact and boards, new boards especially, need to provide basic reasons why characters would meet, interact and plot together.