What I can say on frame recognition is the same other have already reported:
the app (at this point) often fails, usually framing only an half frame or a farme and a half.
Focusing is an hard task here; the web says the minimume focus distance for iPhone 7plus is 80mm,1mm less and it starts to get blurry,I’ve used a plastic box to hold the device to the correct distance BUT the (my?) films are a little bit curved than the plane son the central part of the film may result to a shorter distance and blurred.
To avoid this I’ve both tried to increase the film-device distance and to kee pt film flat framing it with some plastic.
increasing the distance does not fully solve the problem (you still have different distance between lens and different film areas)
keeping the film flat using plastic strips may somehow interfere with the frame recognition feature of the app (indeed I’ve not been able to get any automatic recognition when using plastic strips to hold the film flat)
I suggest to use a support that holds the device something like 85mm from the plane.
