What ist the difference between "External Feeds" and "Newsflash Feeds"?

External Feeds are grafically not controllable. That means that the feed looks like it was provided from the external website after including it in a story. If you know CSS you can affect the layout a little.

Designing Newsflash Feeds is much easier because you can use feed templates and controll the number of feed items and the number of words. You have a ample scope of creative work.