I asked the same question a while ago, but no one seemed to have an idea about it (rightfully). So I started playing with Miss-Input at maximum and have come to a conclusion now after many test matches with new patches as they have came.
The thing is, it lies in the name itself rather than the confusing 'description line' - Input Influence
So, the lower the value, lower the influence is given to whatever we input, on the shot which is played and higher the value, higher the influence our input has on the shot being played out..
Initially when I switched from default hardest of 20 to the max of 100, shots felt rather easy, it felt as if everything was flowing with batting to the point I was thinking whether I should turn it back down but I persisted and results were Brilliant, every shot came down to whatever I was inputting, meaning every four & dismissal were due to my input rather than 'randomness' from the game..
I guess that initial 'easy' feeling when we switch to higher Miss-Input maybe because we're so used to playing with that randomness in our higher difficulties that we actually don't know how it feels to have full control of shots.
Right now, I've settled down at 90 for both the Miss-Input & Skill values, since 100 sometimes does few annoyance like sliding & ball going through middle of bat..
Such a crazy Game-changing value sneaking right at the bottom of the list
TL DR :
Low values > Less user controlled shots > may give sense its harder
High values > More user controlled shots > Initially may feel 'easier'
Although, if your playing on Rumple's values you might have to ramp up your main batting stuff like shot timing, footwork etc., to better suit the higher values..