The question is a bit weird to me because the things you suggest seem like what you would do before you even apply. But when you say "before they take a job there", it seems to imply after the interview, and offer on hand.
When you're interviewing, you're not just letting the employer assess you; you're also assessing the company and the team. You should be asking questions about working there. There's no need to "email people who work there" to ask because you should be asking them during the interview!
My current job is the first time (out of 6 jobs over 14 years) where I am joining a company without anyone I know there -- as in, I responded to a recruiter pinging me, interviewed, and got an offer. I didn't have a friend refer me or anything. It was a risky leap, and made more risky by the fact that it's fully remote (my first remote job), so I had no idea if it was going to be like everyone being overworked, or feeling completely disconnected, or anything. One thing I did that may have appeared weird but was worth doing was, after getting an offer, I asked to speak with yet one more engineer on the team, in a sort of reverse-interview. I extensively asked about working there.
Like someone said, because people don't want to risk their jobs, most of the time they won't say anything negative in such a scenario. But as long as you learn to read between the lines, you can still get useful information out of it.
On the other hand if this is before you interview, none of this matters. Just go interview and decide from there.