If you weren't so set on getting a new camera, I would say stick with the D5200 and start learning a lot more. Every single one of those shots can be done on the D5200 just as easily as on the D700. The D700 doesn't "create" the photo you see. That's new photographer mistake #1: They see a photo they like, and they assume that makes the specific camera good. That is absolutely, 100% not the case.
*DO NOT* purchase a camera based on photographs that impress you. That would be like
Whether he shot in JPeg or RAW is somewhat irrelevant as well, given the context and open-ended nature of your question. Shooting in JPeg will reduce how much editing you need to do, but it will also significantly reduce the amount of editing that you can do. Shooting in RAW will always be the superior option. Regardless, I assume you're looking to capture photographs that look like what you see, and so you're trying to copy the camera, and the settings... and it's not that simple.
Based on everything I have read in this thread, I think the D700 would be an absolute mistake for you to purchase. The D610 will have much better resale value... that's going to be an important factor. The D610 will also perform better. I say go for the D610, since I figure if you get the D7200 you'll want to upgrade to FX after that. The quick assumption often is "Well, I didn't get the better FX camera, so that's why my images just don't have that oomph". That would be an incorrect assumption for most photographers.