And agent is not the same as informer. Whether it's better, worse, or the same is up to you.

"And agent is not the same as informer"

The difference is not really clear in reality and can get blurry quickly. Informants can also be ordered to do more active things to get information - or spread missinformation, or be ordered to do other active things. Simple things like luring a person to a party, or using their influence of position to prevent or make something happen (punish/promote a student/worker, make a certain result go away, ..).

So the majority were likely passive informants with the job of writing reports, but not all of them. And to me it rather would matter if they took the job voluntarily or were forced to do it.

Agents vs informants is a venn diagram. Some informants become active participants under orders of an intelligence officer, they are instructed to use their access for further tasks. Some agents infiltrate groups and inform their handler on group activities and membership. Not all agents inform (they may perform things like sabotage or murder) and not all informants are instructed to do anything (they are paid and never contacted again).