could miniart dioramas be matched together?

I think you will be hard pressed to get any cheaper than the Mini art ones. And I don't think you will get much better either. The buildings are the best I have seen, far better than any plaster ones and a lt cheaper as well. As for matching them, I guess it would depend on the road surface, if it matched up.

You might be better off getting separate road, path sections and picking a selection of buildings and putting your own together.