I try to keep my cirkut #10 images around 54 inches long or less. Even thought factory spooled film is slightly longer, the main reason is the ease at which a picture framer can mount and frame the photos. Matting material comes in a standard oversize of 40" by 60". We cut the board into roughly thirds (13 and 1/4 by 60). This works out to about a two inch mat around the image or a little bigger if cropping the top or bottom is needed. For sure it is possible to make longer photos (the #16 gets really long), but if you are trying to make affordable art that sells easily keep the mat board in mind or it gets expensive to frame.
For group photos, a 16" lens seems about right for a mob of 800 people or less. If you want closer views of individuals you need to use a longer lens and cover less degrees in the pan or move in closer and use a wider lens. Since every photo is different, you just need to know how many degrees per inch each lens will use. A good rule of thumb that Dick Fowler in Florida came up with was to take the number of teeth in the pinion gear and subtract 1, that gives the degrees per foot of film used. I haven't trusted that formula, and it could be plus 1 instead of subtracting. It should be easy to measure and calculate I just haven't spent the time.
Most group work looks better if it is not a 360 degree image but something like 180 or less to 240 degrees. If I want to make a 360 image, I use one of two lenses, a 6.5" wide angle dagor, or a 210 symar. The 6.5" dagor must be mounted backwards inside the camera with a special lensboard and the bed of the camera has to be lowered. As well the camera has to be raised on the turntable and an extension shaft added to the pinion gear. The 210mm lens doesn't need that, but some you will lose a little of the lower part of the picture because the bed gets in the way.
Of course everyone has their own way of creating imagery, this is just how I do it.
BTW the pinion gear for the 6.5" Dagor has 107 teeth. That is getting about to the limit of room for the ring gear to mesh without the whole camera falling over from being out of balance.
Ron in Alaska