My set up is pcquilter, HQ16. I only do end to end patterns.
On leaving the quilt alone while it quilts...I never do that. If bad stuff happens while quilting, you will not be there to catch it early and fix it before there is too much damage to the quilt. This is especially important for the top most and bottom most rows of a quilt, and for starting a row and ending it. Sometimes the hopping foot decides to slide under an edge in stead of over it. If you are not there to stop or catch that - oh, my, what a mess! Ask me how I know....
However, over time i have become accustomed to the sound of the HQ16 happily quilting. I keep my ears tuned for changes in the sound; if it changes than I know I have to check the quilt. Nonetheless, I am still in the same room with the LA, piecing, pressing or cutting.
As with any pattern you free motion into a quilt, the length of time it takes to quilt a row is dependent on the width of the quilt, depth of the pattern, and how detailed it is. Personal observation is that with a computerized system the speed of quilting is less dependent on the speed at which your LA can stitch, and more dependent on the relationship of your quilting robot speed and the machines stitching speed. The quilting robot rules - at least with the pc quilter - so ask if you can bring a sample to test the qbot speed before you buy. I think that is especially important if you can free arm at a relatively fast pace.
Good luck!