I truly believe some of it depends on the machine you have. I currently have two different brands, also used to own a third brand, and each one behaves a little bit differently. With some of them I have better control over going fast, some of them going slow, some with the stitch regulator on, some with it off. I also once quilted on a friend's machine, WELL know, highly advertised brand, and it looked like a kindergartener quilted on it!
And this was after I had 5+ years experience and had won awards with quilts quilted on my machine. Try different speeds, with/without SR, etc, and see if you can find what works for you. And it also takes experience - the longer you do it, the easier it gets, so don't give up! Just practice, practice, practice!!
Andi