It would be extremely useful to have a option to throttle down number of writes during X amount of time for mongorestore.
Currently, there is no way to throttle down mongorestore throughput, hence it presents an issue to restore anything to a live system, as there is no way to control emission rate of the records.
As well as that, --numParallelCollections has no impact if the dump job has more parallel collections than restore job, see https://github.com/mongodb/mongo-tools/blob/master/mongorestore/mongorestore.go#L306
Based on internal discussions we believe that we're appropriately using the max amount of resources possible to drive these tools, so probably not much benefit to any dynamic tuning.
Based on our internal discussion, we believe that using maximum amount of resources is nice for benchmarks on localhost. The benefit is obvious if mongorestore is used against any kind of live system, for the sole reason of availability.