gtd,

Your answers cab be found with GardenWeb seaches. Put in "Bonsai Soil Mix" in the search block top right. You will be able to read several threads and what makes good bonsai soil. Second question, you need to specify what trees you are writing about. Since Bonsai are just trees in containers, you can search the container forum as well for care of certain trees you care about. What City is closest to you (Zone 6b).
There are seven types of Castenea (Chestnut Trees) which type are you describing. In my opinion, all would do fine as bonsai. Check out this link:
https://www.google.com/search?q=castenea+bonsai&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
Aloha