I know similar questions have been asked but I think my case is a little bit diffrent.

Let's say I have a computer with 8 cores and infinite memory with a Linux OS.

I have a calculation software called Gaussian that can take advantage of multithreading. So I set its thread count to 8 for a single calculation for maximum speed. However I really can't decide what to do when I need to do run for instance 8 calculations simultaneously. In that case should I set the thread count to 1(total 8 threads spawned in 8 processes) or keep it 8(total 64 threads spawned in 8 processes) for each job? Does it really matter much? A related question is does the OS automatically does the core-parking to diffrent cores for each thread?