My tag....probably like most... has a switch with two positions. When turned off the tag never lifts and when turned on will automatically lift when the speed drops below 5 to 10 mph and in reverse. The problem with the auto use is that the tag uses a lot of air and takes a while to left clear of the ground. The extra 8,000 lbs of wt transferred to the drive axle causes the rear of the coach to drop until pressure rebuilds the ride height.
I honestly can not see much difference in turning radius either way but having it up certainly eliminates the tag tires skidding sideways. What I did notice is backing into my driveway with the tag up the rear can drag on the up-slope more than I like.
Steerable tag...guess it would be OK but it would not be on my list one way or the other.
Now I almost never use the lift unless it's really tight maneuvering.