I don't have the same machine as you do. I have a Janome 6600 - which I love. I am far from an expert, and I am still trying to find my "groove".
When I started I used my foot pedal and I could go pretty fast. But my foot would change speeds a lot and then my stitches were different sizes and I got a little messy (sometimes a lot messy).
The last 3 that did I unhooked my foot pedal and used the start/stop button. I think I like this better. I can pick whatever speed I want and it will be a consistent speed. One quilt I went slow because I was doing snow flakes when I did my loopy loops I could go pretty fast.
I did have some shaking, but I think that was my table not my machine.
I have found that my machine hates coats and clark thread too. I almost always use King Tut thread to quilt
Good luck and have fun