So if you use your own theme then you got simply no styles definition
a) Yeah, That's pretty much the point, you're the one defining how it looks, and for a css guy blank slate with some basic html is way way way better than having to write heavy selectors or excessive use of !important.
b) Something like....Aaaa THIS!
I dunno, personally...I'm a firebugger. Put everything into a page and just change the styles that need changing by inspecting with firebug...makes for less CSS than styling everything.