I used a bob yak on the off road coast to coast last may,Once you get used to the slight drag,the trailer becomes hardly noticable.
I would recommend using a hardtail with a trailer as the loading on the seatstay dropouts causes wear on some full sus designs.
On Off road climbs i found the low centre of gravity actually assisted grip to the back tyre,this felt odd at first but i was amazed at what i could climb on some really steep stuff in yorkshire.
I used a slightley fatter back tyre to spread the loading as well.
It was really nice to ride with everything on the trailer,i usually ride with a camelback so it increased the enjoyment factor because of this.
An exellent peice of kit,but i would be familiar with your route, before you use it on a ride as they do have their limitations!you can easily detach them if you wish for really difficult parts but if you have to do this you have chosen the wrong route imho.Its note really what the trailers are about.
Steep downhills were also “challenging” and i found utilising the terrain as a natural brake, rather than relying on the bikes brakes was helpfull,i was carrying around 15kgs of gear at times!
Also,i think its important to ride either solo with a trailer, or in a group, as it is an obvious handicap riding with one.
There best used for long, low level off road Bothy/camping trips imho where heavy loads can be carried in relative comfort (compared to a rucksack)for multi day epics.
Just avoid the bogs and really technical stuff!
Enjoy.