There are a couple of ways to use an offset, one of which is to do it like bushhogging and start on the outside edge and just circle in a counterclockwise direction till you get to the smallest circle and then you have to pick up and turn. Turning to the left will pull the disc blades out of the ground if you turn too sharp so you have to moderate the turn. I could never turn them (7 foot wide one) sharp enough to go right back down the way I just came without cutting about 30 feet of turn row on each end (about 2 round trips wide). When we went to 4 row equipment we got rid of the offset disc in favor of a heavy 14foot wide tandem tow type and with those you can turn straight back onto the next pass. 5-6 MPH(about a good trotting speed if on foot) is about ideal disking speed as it turns the soil without throwing it into a pile, isn't too fast that it pulls the disc out of the ground but still fast enough to cover lots of ground.
I have an 8 foot tandem 3 ph disk that I use here in my rocky hard clay type soil. It is really too small for my 70 HP tractor but it is as large as I need. I bought it when I had my 45 HP Yanmar and it was all that it wanted. I pull it with the LS in M range, 1st gear and throttle back to 1500 RPM which is still pretty fast for our rough ground and rocks so it sounds like someone is back there pounding on the blades all the time. I disk about 2 rounds on the ends either before starting or after I finish an area to cover the area that is required for me to turn my tractor. Turning on the ends is when I miss the old ag tractors with the torque amplifier transmissions (dual range power shift) which reduced your speed by half then when turned and straightened out, just bump it back to high range. With my tractor, I have to throttle back to slow down.