I could be wrong, but here's my impression: The two-link rule I think you're referring to is from way back and the limit is two links pointing to the same domain.
Then recently, in addition to the Amazon and eBay limits, suspicion was cast on news capsules; I've stopped using those almost entirely now. RSS would be similar, I believe, but not so widely syndicated. Link capsules are like RSS, but not dynamic, so they would look more like duplicated material, too. So, of those three types, RSS is safest.
You will notice that HubMobs (and similar) are still using an RSS capsule. I believe there are two keys in using the RSS capsule safely. One is to use the "first-sentence-only option" in order to limit duplication. The second is to make the target of the RSS as pertinent as possible to the hub. I've stopped using scatter-guns like "more of my best hubs." Google is smart enough to tell that's irrelevant quackery, but that //birds/hot?rss contains some loosely goosey things.
Usually what I'm doing now is picking the //hot?rss from the category in which I have placed the hub. If I use //best?rss, it won't refresh very often unless it's a big category. If I use //latest?rss, it won't filter out the low-quality rubbish.
During the contest month, I am appending one (only) additional RSS link to those I mentioned above. This will refresh every few minutes during the contest. In May, I will remove it from my hubs: http://hubpages.com/_hsrf/tag/writingcontest/latest?rss