It would be great if there were a doc explaning what each Alert Event Types means (and even that could give us some examples). And the same documentation should explain wich alerts have thresholdconfig or metricthreshold_config.

The documentation that I have found with a little explanation is thw below (and it shows some alerts type that don´t work)
Example: OPLOGBEHIND => When trying to use this one on terraform, it returns an error saying it does not exist (the one that works is: REPLICATIONOPLOGWINDOWRUNNING_OUT)

https://www.mongodb.com/docs/ops-manager/current/reference/alert-types/#user