Great questions! I'll try to answer as best as I can.
It is acceptable and fairly common for people to create new accounts for a specific project and pick an account name the reflects the project in addition to having their own personal account.
Witnesses run the servers that are the distributed infrastructure of Steemit. They also help to maintain and vote on the code that runs Steemit.
I can't say, since I've never attended a meetup. But @papa-pepper has posted extensively on meetups, having attended several and even hosted one or two. Check out his posts for tips.
This will help greatly as I grow in the community thank you so much!
You're welcome.