Arnoldtailor

Try making a new type of wall that has the cladding you want and just use it where you need it, like around the windows. If that doesn't work, use small soffits or slabs instead, and be careful to fit them around the windows without blocking them. If the snapping is the problem, see if you can turn it off for a bit so you can place things more freely.

Regarding the inner walls, yes, you can also use the software to auto-generate them with horizontal 2x6 boards attached to the main poles. This feature can save you a considerable amount of time and effort as you plan out your pole barn.