Im not sure about the first question. However, regarding the second one, I believe that it will lag no matter how many feeds you have in the feeds and notification screen. I would download the stable version of fasterN9 http://talk.maemo.org/showthread.php?t=83940
and the lag on the feed screen would rarely occur no matter how many feeds you have. Also your phone would run smoother than ever.
Just my 2 cents.