Am I right in assuming that if I run launcher I no longer need my M20empacman, M21emptris etc, but I keep my N01mount and N10telnetd scripts?

That's correct. If you want to start/stop telnetd from launcher, you'll need something similar to the provided N02telnetd script in the distribution, but it's not necessary to make it a preinit.d script. I just chose to make my preinit.d script do double duty so that I didn't have to have two scripts.