Will I have to choose my seat at purchase time during the week? FYI I like choosing my own seat based on who is next to me. I don't want to sit next to a bunch of noisy teenagers or young children.

If it's the reserved seating, yes you choose at time of purchase and your tickets will have specific seat numbers

You choose your seat at time of purchase. If you have an issue with people being noisy, tell someone. That is what the ushers and managment get paid to do.

Almost all movies are shown in some theaters that don't have reserved seats. Imax being a notable exception.

Yes, they show a graphic of seats available vs taken, so you try to pick seats away from currently sold seats, but that doesn't take into account everyone purchasing after you.

The answer to all of those questions I would say ask when you purchased your ticket cuz I know I don't want to sit next to any teenagers all noisy kids or people being on the phone