Some SNAP processing will use multiple cores if they are available.
Calculation speed is a function of CPU speed and number of cores used, but also I/O and memory. There are so many different hardware configurations that you probably need to investigate the effect of various tweaks yourself. Often, remote sensing involves similar calculations on many data sets (times and areas). Because there is usually diminishing returns using more CPU’s, it is often to configure a system to support more calculations on different data rather than focusing on speeding up one calculation.