In the CBS show Mom, why are some AA meeting in a circle while others are just a traditional meeting with a podium?

I am guessing depending on the number of attendees who are at the meeting. The number of people (if lets say 10) more likely to be in a circle. If 30 or more, podium would be better - the circle would be too wide and less intimate.

All meetings are Different! there are different formats and Set up- Each Group Makes up their Own Format

Crowd size. Where the meeting is held. It doesn't have a meaning.

Each AA chapter is semi-autonomous. Each make their own rules and work out what is best for that chapter. Seating, smoking, refreshments some rules of order are all determined by the "will of the group" . Meetings held in the same space can have different rules. What doesn't change is the common goal Sobriety.

Because it depends on point of the scene.