I also used the GK trick but not much.
The result was the same.
But it's good I think if you want ot improve only shooting and finishing skills for a ST.
1. Is it going to happen in the same manner If I were to use only pass, shoot & go drills? If were not using goalkeeper drills would my CDM gain passing twice as fast as shooting or speed?
no, it won't be the same.
Luck is on factor and a hidden queue as in old version was.
It's Passing, then dribbling, shooting, finishing, passing again ...
If you 're using a normal set, it depends in what skills every drill has.

Yes, the white skills gain more but I don't know if twice is number.