Please share everything you know about the breed. If you have pictures feel free to include them.
I'm mainly interested in how they would do in low level dressage..
They can do low level and much much more....
Look up Cottonwood Flame on the internet. Dressage Stallions; Portmanteau, Brentwood, FHF Thunderstick (Thor),Carrington, Vance, Cottonwwood Flame
He was Grand Prix level dressage. He had a Piaffe equal to any school master I have seen. If you are interested in dressage look for a modern built Percheron. The kind they would use in the big hitches. They are less bulky and a little leggier. Sort of the appendix quarter versus bull dog quarter of the Percheron world.
Percherons have a natural athleticism and almost catlike shoulder freedom. My mare can lift one foot up and out and rest it on the middle rail of her pipe corral when she wants attention. They have a little too much action for some dressage thinking people but I don't care.
In the 1800s they were the horse of chioce for hauling big wagons on the docks for a reason. And for pulling the fire engines.... They have a reputation for always knowing where their feet are. I saw my own girl back out of a wood pile stepping over logs when she couldnt turn around to get out... she had gone in there for a tid bit to eat.
I have heard some people write they wont canter. Oh they will. I have pictures of My mare in full flight with my trainer aboard. Julie says she has a rocking horse canter. If the horse was originally trained to pull a carriage or cart he was discouraged from cantering. So it may take some practice and encouragement to get it.
There are some limitations to the way you can condition them. They have more short twitch muscle the kind of muscle for strength and less long twitch for aerobic things like running. Conditioning for endourance has to be taken slow and care made to keep them from becoming over heated they don't have an efficient cooling system. But once in condition it taks just a little mantinence to keep them that way.
Good Luck with your dressage search