Wifi connectivity has no bearing on the quality of the scan. I have done numerous scans for Professional & Elite Level College & Junior players in rinks / locker rooms that had no wifi and uploaded as soon as I got back to the hotel. No issues at all. The only time internet access is needed is to upload the scans via email and create a profile online via True's portal.
The scanner calibration app allows you to move the box being scanned relative to the actual subject. It takes some time, but ensures maximum precision of the object being scanned. This alongside communication with True in uploading of Test scans makes for a very thorough process, as long as you take the time to do so. This is more intricate than any motion capture protocol you might come up with since more human error is reduced.
In my experience, as long as your lighting is not drastic, you will not have any issues. Obviously an area that is either too dimly or harshly lit will not allow the scanner to operate properly, but you will see that visibly on the screen because you will not be able to see the foot. Any neutral lit room with standard lighting will suffice. I have done fittings in store, at rinks, in hotel lobbies etc that all come out perfect.