You don't have to be well-organized nor strategic. Being chaotic and uncaught often works. I listen a lot to Behind the Bastards and Lions Led by Donkeys. It has given me the impression that effectiveness of a given behavior is a horseshoe, where the ends of the shoe have greater impact than a balanced style.

Only need the organization level of a WW2 resistance cell or an IRA cell. Squad level is more than large enough to execute effective operations on a strategic level so long as said cells aren't entirely singular, 5 cells each with 5 people for example even when working independently could probably bring a cities infrastructure to its knees let alone kill random politicians and their buddies.