In short: each boot will use its own kernel (and OC settings), so while Fremantle boot should support KP50 and OC settings I have really no idea if Nemo's one does (most likely, nitdroid comes overclocked to the max iirc for example). This question should be asked in the Nemo thread (but not the release/announcement thread, use discussion thread for problems/features discussions: http://talk.maemo.org/showthread.php?t=80361)