Answer 1
It usually depends on how the trailer is loaded. If you put a lot of weight on the back of a trailer, you can create negative ratchet weight and the trailer will lift the rear wheels of the towing vehicle, perhaps enough to cause you to lose control when descending.
In general, a single axle trailer is more sensitive to load positioning than a two or three axle trailer. We have several horse trailers, and they are all twin axles because the horses tend to move around in the trailer.
answer 2
Front heaviest trailer