The enforcer drone is a heavy assault hive ship that harasses enemies while calling for backup from a few elite assaults (elite, being those alternate-AI assaults capable of traversing sectors to chase an enemy).

Enforcers either spawn around minor derelicts (see next suggestion) or at a low chance where the passive guardians spawn. They'll attempt to find a target, who they will fly slow circles around, usually around 1km. The bot has a single hive gat as its main armament, but also has a missile turret it uses to blast its enemies from afar. As long as this bot is in a sector and has a target, two elite assaults will be called to the sector, a maximum of two per local enforcer (not including any that are already in the sector).

+1
Also, will they follow you into a wormhole sector or a guarded sector?

Debatable; I don't think the enforcer itself should follow fighters, but ought to follow capital vessels - a sort of threat prioritization given to it by the Hive overlords.

Also, guarded sector? Those don't exist in the current outer region. And, no, I don't think ANY hive bots should follow you across any wormhole itself, at least yet. We'll see what the devs plan to do with future outer regions (it might make sense then!); as for following you to the inner region, no, I feel the hive would rather defend areas it has set up strongly in compared to areas that are effectively highly dangerous to them.