IMC, we play all the different hench-types differently.
A cohort or familiar works like an extension of his parent character, subject to DM veto. The player gets to fill out the character sheet, decide on combat actions, and even roleplay him, but the DM gets to override any decision that is totally unreasonable in context. ("No, your second-level wizard cohort does not try to bull rush the Great Wyrm. Pick a different action.")
Followers are treated as independent NPCs. The PC has a special relationship with them and gets to give them orders, but the player doesn't have any direct control; the DM decides whether and how the orders are followed. If you order your Expert2 follower into combat, he'll probably refuse. Put him in danger too often and he'll probably leave you-- and be replaced by a Warrior follower of equivalent level.
Animal companions are also different because they don't have human minds, and communication is harder. Most of the time, the PC needs to make Handle Animal checks to make the animal do anything specific, and that's limited to the "tricks" that skill can accomplish. If the PC is wildshaped or can otherwise speak directly to the animal, he can order it around like a follower, but its intelligence still limits it to simple tasks.
A cohort or familiar works like an extension of his parent character, subject to DM veto. The player gets to fill out the character sheet, decide on combat actions, and even roleplay him, but the DM gets to override any decision that is totally unreasonable in context. ("No, your second-level wizard cohort does not try to bull rush the Great Wyrm. Pick a different action.")
Followers are treated as independent NPCs. The PC has a special relationship with them and gets to give them orders, but the player doesn't have any direct control; the DM decides whether and how the orders are followed. If you order your Expert2 follower into combat, he'll probably refuse. Put him in danger too often and he'll probably leave you-- and be replaced by a Warrior follower of equivalent level.
Animal companions are also different because they don't have human minds, and communication is harder. Most of the time, the PC needs to make Handle Animal checks to make the animal do anything specific, and that's limited to the "tricks" that skill can accomplish. If the PC is wildshaped or can otherwise speak directly to the animal, he can order it around like a follower, but its intelligence still limits it to simple tasks.