I think most people are good with Streamline. Arthmoor mentioned a good idea to take care of the extra SL does not do for cell transitions. http://www.gamesas.com/index.php?/topic/1085073-relz-map-marker-overhaul/page__view__findpost__p__15817907
Don't know; I've seen a lot of criticism over the last year of Streamline. I tried it, briefly, and never noticed a difference. But since I'm running (like you) a lot of script-heavy mods, something that purges buffers from time to time would seem useful. And if the mod delays buffer purging for X seconds, all to the good--unless, of course, you decide to switch cells at that same X number of seconds.