"I still want the category pages to distribute their link authority to the individual pages, then I should leave the category pages in the site map and meta noindex them, rather than robots.txt them. Is that correct?"
This will achieve the goal, yes. You would ideally include noindex, follow (as opposed to nofollow) in the meta tag of the page you want to exclude. This means that Google crawls the page in full and allows PageRank to flow from that page to the pages it links to, but doesn't include any of the page's content or its URL in the index.
If you exclude the page via robots.txt, Google never crawls the page at all. You sometimes see URLs whose pages have been excluded via robots.txt showing up in Google's index, because robots.txt doesn't say "don't index this URL"; it simply says "don't crawl it." That's also why excluding a page in robots.txt and putting a noindex meta tag on the page would be redundant - Google would never see the noindex tag because it would never crawl the page.

