My experience may be different than that of others for a couple reasons: 1) I'm an instructor, sometimes with students, and 2) I dive with my camera and don't stay with the group very well since I often stop to take photos and try to get the perfect shot. If I am teaching, the DM's have been "hands-off" and let me keep track of my students. Generally, they like to be able to at least see everyone's bubbles so that they can keep an accurate headcount. I can't say that I ever had the DM's insist on folks staying really close together, but then most of the folks I dive with are pretty well experienced and the DM's picked up on their skill levels pretty quickly.
Our groups were usually spread out comfortably both distance and depth. The DM gave a recommended max depth but didnt micromanage anyone. It generally was a good idea to stick around the DM so as to be able to see any neat stuff such as seahorses that they may point out. They are pretty good at banging their tanks to get everyone's attention if they see something interesting.
If you're a competent diver, the DMs that I had there seemed pretty good about letting you do what you wanted so long as it was safe.
Water temps I had in late February were around 78-80.