If your tractor's tires and weight combination is appropriate, AND the snow depth is under 12" lets say, you can easily handle a 7-1/2' blade angled at 30 degrees. I have a 1070, mechanical 4wd, ag tires, loaded rears and can push snow off my dirt road in high gear (9th). To me, the optimum blade length is one in which a down and back pass on the driveway is the full width of the roadway. Plowing doesn't really take that much power. It takes quite a bit of tractive effort, though, however you arrive at it. You can go too slow, also. In that case, snow/slush friction can become a problem getting going. This includes the possibility that you have a gravel driveway in which case, catching some gravel makes life more difficult. Once the plow is churning though, you can get some speed up. It also depends on how good you can steer it. If you have a loader mounted plow stuck way out beyond the front wheels, maintaining steering control at high angle and high speed can get you into trouble. Yes, some people go slower than Gramps leaving the bathroom when plowing. That's all they can figure doing.
You might also consider where your rig will be parked. Getting through a door and parking your machine in a manner to not interfere with all the other garage activities can be an issue. Some folks believe in tire chains, too. But, I mounted my truck plow as close to the front wheels as I could get it. Believe me, snowflakes fear my name....
