Here's some of the church hierarchy, hopefully others with HQ experience can fill in the higher levels.
Congregation
Elders are overseers of different departments. The presiding overseer or PO chairs every committee and is in overall responsibility. Generally, he is not a boss man, because decisions are made by committees, but a politically astute PO can more easily rule the roost than other elders. Elders are made by being voted (I think unanimously) by the other elders in a secret session. All elders meetings are secret.
Ministerial Servants are just sub-elders doing less spiritual matters, small speeches, perhaps shepherding the flock. Usually one handles literature accounts, another money collections…
Publishers are men and women, and kids (if active on door-door and approved of). This is 'drone' level. They report their preaching hours on form every month. This is compiled by congregation and sent to the Branch, then Brooklyn (supranational HQ)
Circuit
City overseer is the travelling circuit overseer's mailman, he also helps co-ordinate assemblies for the circuit.
Circuit overseer (travelling). These men used to all be single, now they are virtually all married. They manage about 20 congs (that's maybe 800-2000+ people depending on area) . He gives pep talks, door-door demonstrations. Behind the scenes he handles the elders, rubber stamps their new appointments usually - not always. He will have contacts at the Bethel branch office (National HQ) and must report on all the congregations. Some COs are political lightweights, pussy cats, some are serious Rutherf…..rs
District
The district overseer manages a few circuits (does anyone know the average number??). From a publisher's eye view, this man is a public performer who only appears at assemblies and addresses thousands, only to disappear until next year. I believe his responsibilities have as much to do with Branch HQ departments as with his district. When a tricky apostate matters comes up, a CO and DO are often despatched 'for a chat'. In my locality, two such men arrived unannounced at a congregation meeting once, just got onto the platform and announced that the congregation was dissolved, not the meeting - the congregation! So these guys are major ball crackers.
Bethel Elder
(From here on it gets really hazy for me.)
This is not just a congregation elder who happens to work at Bethel. He is of a very much higher class. Help, Maximus! Or other Bethel insiders, can you fill in some detail.?