I use Mach3 and an IP/M on my router and have never noticed any jerkiness on curves. Don't know if that is luck or the right settings! I've been using F360 with various cutting strategies recently, some of which use a large number of short straight line segments which Mach3 seems to handle ok. So it seems ok whether or not G2/3 or straight line segments are used. I am using steppers rather than servos and it does seem possible that servo tuning would have an effect here.