My experience has been that the overall culture and atmosphere at larger universities is relatively unimportant. You will encounter it a lot less than you will the culture of your research group. There's also going to be enough chemistry grad students that you'll likely be able to find a group you get along with.
Ideally, you shouldn't go anywhere (imo) that you don't have at least 3 faculty members that you feel are good potential mentors. You can't get a perfect feel for someone until you're in their group, but through talking to them and their students/post-docs during a visit, you can get a pretty good idea of what they're like. Having 3 people & groups that seem reasonable after meeting with them means that 2 of those groups can not work out and you'll still be OK.
Also, the question's you're asking here are things you should be asking the graduate students on your visits. You get a lot more (and better) information talking to people face to face than you do online, and it's a lot easier to pick up on subtle cues that way.
Back when I was applying to grad school, it was pretty clear after visits where I felt like I'd fit best, and where I felt like it would be a stretch. That's the whole point of visits.
Take notes while you're there, and then at the end sit back and visualize where you felt most at home, and where you felt most excited about working with a group of people. Hopefully those are the same place.
