Re: equivalent distance or height into miles....
Mapping Software uses the traditional tried & tested method of Naismiths rule to calculate journey time.
e.g. The "flat" mileage distance for given miles per hour hour, then just add an extra time per 100m of height gain.
You could, as I said, then work back and use the final time to find out how far you would have travelled in a straight line on the flat in the same time.
Mapping software does not provide a true distance.
That can be got by knowing horizontal map distance, height gained, and then apply basic right angle triangle Pythagoras to find the length travelled up a slope.
Or... height gain, angle of elevation, and apply basic Trigonometry.
(A mirror sighting compass, or a Theodolite, can do this... you still need to do the maths though!) .