I have one thornless blackberry bush. So, I'm not an expert but I can tell you what I experienced. The first two years it grew well but produced no berries. I learned that I had it in a wet spot. So, I transplanted it to a much drier spot...and then totally neglected it. So, it has grown very slowly and produced only a handful of berries, but actually it's quite hardy considering that I always forget to water the darn thing and it has survived even a dry summer like this. It's green and growing amidst brown, dry grass.
The branches are very woody and much stronger than the raspberries I have. There are much fewer branches and fewer berries, but the berries are big and very tasty.
I think it'll grow very well on your fence with a bit of work to either thread the branches in and out of the fence or tie them to the fence. I don't know how much shade they'll actually produce, though. I wouldn't call my bush a shade bush at all. I have it trellised along my fence and it produces far less shade than my grapes, raspberries or apple tree, for example.
If you really want shade you might consider some grapes. Those trellis well, grow rapidly, and produce very big leaves.
Good luck!
