I've had a Bernina with 9mm and have had these issues that I've solved for me by doing:
For the 9mm, doing a 1/4" seam, this is my solution; using the #1 or 34 foot, move the needle right to #3or4 (sorry I forget) & place the material to the right edge of the foot. This way the fabric covers the feed dog.
I think when I've done tight curves I've used the #8 foot
Because the 770 (with 9mm) has a larger throat, I'm considering it over the 570. Can't make up my mind. What mm is the 570?
The width of the 770 is <19 1/2" which is too big for most OTC carrying cases. Don't know the 570 measurements.
I think the wts are 28 for 570 and 33 for 770. I'll need to try the machine in my carrying case & see if I can lift it into the car.
Any other comments comparing the two?