Hi Shawnee, I was very happy to stumble across this post. I know just the shows you’re talking about - East Coast (east-coast-horses.com). I started driving in them last year (I work in the office as well). I did exactly the same thing you’re thinking of. I bought a Jerald cart that will let me do these open shows as well as APHA breed shows. The cart you’re looking at will be perfectly fine for these shows, spoke wheels and all. We have everthing from saddlebreds, to hackneys, stock breeds with “Jerald type” carts and several folks with “real” carriages. It’s actually a very congenial group of folks that all get along and manage to show all these different types together and still have a good time. The main change from your breed rules will be having to carry a whip as they do enforce that rule. I don’t bother with the apron, nor do any of the others showing in the jerald style carts. While they do “technically” go by USEF rules they’re rather loosly followed since the classes are small and it is an open show. You won’t be DQ’d from one of their shows over attire. Wear a hat, blouse, gloves & long sleeved shirt and slacks and you’ll be fine. All my attire came off ebay.
Someday I hope to have the money for one of those stunnning carriages and perfect turnout. but for many (like me) the jerald style cart + open shows is a inexpensive learning grounds. My gelding is home trained and my first driving horse. He’s no where near perfect and I’m sure my turnout and cart could be picked apart…but I had an absolut blast last year and can’t wait for the first show this season. That’s all that really matters 
As for the East Coast shows, you may know that they’re cutting their format quite a bit this year. So far they’ve kept driving, but we need all the numbers we can get to ensure that they continue to leave the division in their shows. I really hope you can start driving with us this year!
There are lots of videos from these shows on you tube. Just go there and search for tinafarmer (one word). You’ll see the videos we put up from last year - just scroll through to find the driving classes. The almost white paint is mine.