You said something about his hind end looking odd. What I see is the gluteal muscle is very chunky and round and ties in to the leg rather suddenly and high. The gaskin, below it , is a bit on the lightweight side . Good sized hocks and hock angle is normal. Upright pasterns all around, cannot see feet well enough to comment. Back is nice and short. Although the wither is high, and set fairly far back, the angle of the should is more upright than one would expect with the wither so far back, and I do believe he is a wee bit pigeion chested. In the top photo his front legs seem a bit close, but could be an optical illusion, but it appreas as if he is base narrow in front. Neck is long for good balance and not downhill.
Some good and some not so good.
As far as working cattle, I am told that any horse will benefit from working cattle. I have never had the chance to do this. And for trails, he looks fine. Now, how do you think about his MIND? Since that is what you will really be riding!
ETA post moved to critique section!