The fact that the trunks are red-orange is really the only thing about this that might raise a red flag and imply that they could be different, as mine tends to lean toward brown and gray. I did notice that coloration in the pictures. Elm species are not the easiest things to tell apart when specimens are small though, so you might just wait to let one get some years on it to see what it looks like. Ultimately though, I would guess which species it is probably doesn't make any difference to your interest in working with it.
Mine is in a fairly standard plastic pot right now, but I don't think I'd hesitate to put it in a shallow pot when it's "finished". It has some time to go before that, if it ever even gets there. I plan to eliminate all but a the soil-line level roots around the nebari and then put it in a bigger container to grow. I want to see sizable roots at soil level on this one. That may turn out to be a mistake, but if it is this is the tree I want to make it on.
I'll tell you what I'd do with this one of yours if it were in my care. I'm still pretty inexperienced with bonsai compared to most of this community though, so you have that warning. If I were in your position, I wouldn't follow this advice unless someone far more experienced backs me on it.
First off, I'd probably remove the tree by layering it instead of digging it up. I'd do it this way because it appears to have a straight section of trunk below the burly part and I can't really see that becoming part of the finished tree. Though, digging it up might be better done first just to get it in a better position to layer it. How to layer it this way is best figured out by someone with more experience than I can lend you. What I'd want would be to get roots coming from the bottom of the gnarled part to form a new nebari. At least the tree should be willing, as there should be dormant buds all over that thing.
As for the top, I'd try to make sure the growth coming directly from that burly trunk is not very straight. It has some straight growth on it now and I'd get rid of that. When it starts popping out with new growth, I'd pinch it off initially after about 2 or 3 leaves as if you're trying to build ramification and keep doing that until it gets about 3 inches of nice crooked growth. Then let it grow as it wants to for a while to thicken the branches. But if it tries to send very much of that new growth anywhere near straight up, I'd direct it more downward very carefully after the branch gets a couple inches long. My experience with my own tree has shown me that, while the new growth is very fragile, redirecting it will take within a week while it's growing fast and the growth of the branch will follow in that general direction as it progresses, even if you're pinching it.
That would take you to a point where it's partway trained. The end goal of this would be to keep it stout and make it look completely gnarly, very old, and maybe almost haunted. The finished tree would be very short and wide. The leaves would probably never reduce enough, but I think it would still look very interesting.
As I was saying though, take that advice with a grain of salt. Still though, now that I've said all that, I think I need to try to find a similar piece of stock to try it on.
