rockm

"But then, I realized that there were so many other species (or subspecies) of elm, that is why I was questioning which one....still kinda unsure which one (catlin or corticosa) I will use."

Well, heck, Brent's right. One problem here is that you've confused species with cultivar. Corticosa, catlin and every other Chinese elm cultivar are the same species. They are Ulmus parviflora--chinese elm. They have, for the most part, the same care requirements. The differences are in some of the genetic quirks of each cultivar. With corticosa, its the bark, with catlin it's the smaller leaves and denser twigging.

Your challenge is to find which one offers the best advantages vs trade-offs. All have disadvantages, all have advantages. Again, it's really up to you to decide what you're after in the image you're out to create.

If you want a larger forest, with bigger, older looking trees, then corticosa would work fine--if you can finds suitable larger stock material. If you want a dense twigging and dense (almost impenetrable) foliage pads, the use Catlin.

It's up to you. If it were me, I'd just jump in with some generic (i.e. inexpensive) Chinese elms and see what happens. Go from there.