When I ask a question about if I run too many process will slow down my Mac for Magican measured my Mac is high CPU usage. A Mac user tell me the icons on the desktop may still influence the performance of my Mac. Is this true?

If I have movies, music, document, Photoshop...running on my Mac. I wonder to know whether they will slow down my Mac. I use Magican to monitor my Mac, it displays the programs are take high CPU usage.

If they will slow down the Mac, should I need to cut down some process?