1. If you set up AEB and then hold down the shutter button, about how long does it take to shoot all three exposures ?
2. Is one faster (between the M5 and the M50 ?)
3. What other setting effects how fast the AEB is ?
1. The time could vary slightly depending upon shooting conditions and camera settings. Usually, it happens without much in the way of a noticeable delay.
2. I suggest that you compare their frame rates, fps.
3. Some combinations of autofocus settings can slow down the frame rate, but only slightly. Your lens can have a larger impact on frame rate than AF settings.
When I use my 22mm prime, AEB is super-fast.
When I used my adapted 70-300mm EF, AEB was painfully slow - a couple of seconds at times.
When I do not use AEB, the frame rate with the 70-300 is very fast, so it is not the adapter.
I guess it just takes time to do exposure changes (aperture ?)
I have to test in various light conditions. I noted the very slow AEB in quite low light.
Not that it answers your original question, but I think AEB works by altering the shutter speed to achieve the required under and over exposures. Changing the aperture would mean that you would also be changing the depth of field and affect focusing.
Have you made any settings in the camera menus to make any automatic adjustments for long exposure or high ISO noise reduction, or highlight tone priority?