good points brought up. I think (and it's probably obvious to you too) that Mentality and creative freedom are influencing factors that contribute to the actions the wingers take.
If your winger has high creative freedom and decisions I would try his crossing at mixed and let him make up his own mind. Same with forward runs. Running with ball is obviously needing good dribbling skills but again if he has high creative freedom set this to mix so he can decide for himself.
The mentality side of things is more murky and requires some playing about and fiddling with on your part. I also find it difficult to find a medium with mentality that suits players, this is because we have never really been given a disected explanation of mentality by SI.
But I would hazard a guess and say the less mentality you give your winger the less likely he will get forward which may be what you want if he is going forward to much at the wrong time. Conversely if he isn't getting forward enough then try raising it. You just have to try different things one at a time probably and see if there is any perceptable difference.
I don't know if this helped or if I am just rambling. Hope it does help.