I agree with your thoughts, and do think that "second feed tab" is a wonderful idea! It should be very handy and no clutter. Your posts will be seen, and so could be the shared posts, if one clicks on the tab.
No, I don't think that we need featured author posts when the whole work is being posted, "share" feature would be enough, imo.
But me, for example, I am doing daily top5 in psychology - so am featuring 5 articles at once, not the whole text, and @dragonslayer109 has a whole bunch of articles and links in his hidden gems, for these kinds of featured author posts it's form difficult to impossible to realize everything just by sharing single posts, but I think it's something you meant by ""the weekly roundup" curation type posts".
Where should we propose the "second feed tab" so that we're heard? :)