In perftest, currently, there's only -x <pool_size> which activates both parallel execution plan and sets the session thread pool size. It would be good for benchmarking to be able to set these things separately. I suggest changing -x <pool_size> to only set the pool size (and mentioning that the default is the hw thread count) and add another flag -P (or whatever you like) that only enables parallel execution planning, with default being sequential execution plan.