Re: Am I on the right track?
Welcome to Beesource!
I like Rusty's suggestion about all one size box (I use only 10 frame mediums), but one consideration is that you are buying nucs, not packages. Most nucs are likely to be using deep frames, so figure out how that is going to fit into your plans.
Paint vs varnish is partly a appearance/preference issue, but UV rays from the sun are damaging to wood. Paint is likely to do a better job of blocking UV than varnish, IMO.
ultracrepidarian >> noting or pertaining to a person who criticizes, judges, or gives advice outside of his expertise