While I can't address your specific questions on rims, anyone looking to build their own wheels should also look at the DIY packages at BDopcycling.com.

I used their road kit III to build a set of wheels for my new bike and am very happy with the service, package contents and of course the wheels themselves. As long as you are capable of doing the build yourself (which I actually enjoy) I don't think you can do much better for the money than a DIY kit from either source.