this way you can modify your monsterspawner anyway you want (like make it a mobile Championspawn, or whatever...
but remember im not Arte theres probly like x³ better ways to do it
EDIT* nearly forgot to adress your quesitons...
1) waypoints... hmm you have to keep in mind that monsters ai "freezes" if no one is in range of 26 tiles so theire actually only gonna walk from A to B (on bigger distances) if you guide them on their way
2) sorry i dont get it... grouping them together like in 1 subgroup ?
3)the best about the multi would be to uncheck "clear" in the extenden spawner gump so the multi stays aslong as monsters are living and when the Randomonsterspawner is moved to another location and respawned the Multi vanishes in the old location and spawns in the newly selected one
4)sequential spawning doesnt randomize at all... it gives you the possibility of spawning monsters in differend subgroups and you have to clear one after another to proceed in the spawnerentrys... but thats not all theres various things to play around with