Best way would be to start somewhere and then monitor your system resources and adjust as you see fit.
ROUGH ESTIMATE: from those details you listed, I think you can run 6-8 in parallel, with some delay to start each additional process (for example, start one create plots, wait 15 mins, start the 2nd, wait 15 mins start 3rd etc.).
Things to monitor when you start: CPU usage, Memory usage and the temp dirs (assuming its the 2 m2nvme) how full they get etc.
Good luck