We just use rear panniers. You should not need any more room than they offer. We ve gone from Pamplona to Santiago twice with such rigs, 98% on the trail, with very little pushing.
The trailers seem popular in the US, but I find them to be a heavy, awkward gimmick. We have done much of the Great Divide Route in the US and the BC Transcanada with just an old man mountain rack and rear panniers. Several times a friend with a BOB has joined us.
Everytime, they have gone to panniers and left the BOB home the nest year. They are just not worth the weight and hassle. We just got back from the Colorado New-Mexico portion, and where trailers were nce dominant on that route, this year we saw 9 riders with rear panniers, only two with BOBs. My wife, a middle aged recreational biker, cleaned Fleecer Ridge on the Great divide, and left a bunch of strapping young men with Bobs in her wake.
Don't even get me starterd on lifting them over gates, fitting them in a rental car, etc.
We have found the best rear rack to be the Old Man Mountain. It does not break and has no gear wobble. Expensive, but the last two trips were a clean sweep--all the cheap racks broke.