I am that user above. So here is what I found after investigating into this a bit further, with load test done (which Richard has kindly provided info on how to do this above).
To note, my setup was on Google Cloud using Compute Engines. The load test results are attached as excel file.
Initially, I had Moodle and jobe on
different zones on Google Cloud (e.g., southeast1-b and east1-b). It seems this added
additional CPU load on jobe for some reason - which I still don't know (maybe encryption?), although internal IP address was being
used to connect them, with very little load on moodle.
I put them into the same zone (southeast1-b) and this somehow decreased the load on jobe server while the load on Moodle increased as it should have been. After that, I increased the number of students to see what the stats are like. It seems if I configure them to 8 core each, it should easily (or reasonably) handle 250 students, possibly would work with 4 core each as well.
So it seems after putting Moodle and Jobe on the same zone, I was able to achieve a reasonable performance. A strange find but that is what happened - a lesson learned.
Next step, to figure out how to do load balancing so I don't have to keep Jobe on 8 core or manually changing it.