When I transitioned over from shoes to barefoot, I only needed to use boots on the fronts. I also ride gaited - and those horses will move VERY differently in gait when you first put boots on. Only used the 'emergency trail boot' idea once - didn't work well. Ended up having to walk back to camp. Trying anything faster than walk when a gaited horse is shod on left front and booted on right front was just waiting for a stumble.
Boots have more traction than the average shoe. Most gaited horses move with a bit of a slide when in gait. Especially if they have developed their gait while wearing shoes. The second the grip changes on one side but not the other - they will be off in gait. Some more than others.
I've now been 100% barefoot for 7 years. Not even using a boot. No matter the rock or slope - my gaited horses stay sound and never slip. They've stayed sound even when I was training 40 miles per week. It takes time, the right feed/supplements, rock laid down in front of troughs, and proper trimming/rounding.