Very interesting question… so far, I’ve always used the mechanical shutter on my XT2 when using it to “scan” film negatives.
In theory, the electronic shutter mode would produce less vibration during capture. I’ve never tested this, but I can imagine it might actually make some difference when dealing when using a macro lens to scan film. The downside though, as you’ve said, is that it could also potentially introduce banding in the image based on the light source. So, it might be somewhat dependent on your light source.
It’s definitely worth testing though!
On the subject of blurriness though, I’ll make a couple of points:
Make sure your film is perfectly flat. Any kind of curl in the film can obviously cause issues when dealing with a macro lens. Wet-mounting is the flattest. Using ANR glass is good, but the glass itself can degrade sharpness a bit. The Negative Supply film carriers are the flattest way I’ve found other than wet-mounting and ANR.
Use a mirror to make sure your camera is perfectly in plane - If you’re using any kind of tripod or copy-stand, place a mirror at the base, and then align the camera so that the reflection of the lens is perfectly in the middle of the frame.
On your camera, use focus-peeking and focus check, and adjust the focus manually. I don’t trust the auto-focus when scanning… the focus-peeking and focus check will really make it clear when you are perfectly in focus.
Hope that helps!
Creator of Negative Lab Pro