seeking overview of aggregation plug-ins

I see in the colophon several aggregation plug-ins.

However the documentation in the codex doesn’t really answer the questions I’m asking:

1. Which aggregators extend links? How?
2. Which of the aggregators support multiple categories? For multiple rss feeds?
3. Which of the aggregators use SimplePie?
4. Do any of the aggregators have the ability manage rss on an item-by-item level?

IF someone can point me to sets of documentation, articles, what-have-you, I can take it from there.

But right now, it the features comparisons seem a bit scattered and cryptic.