Nothing too fancy. LTSpice for Windows (although replaced by current version for macOS), old SwitcherCAD stuff and PSpice. The really heavy luggage is Altium Designer 20 with integrated Spice simulation and also the 3D PCB viewer. Works way faster on my M1 air (Parallels 17, Windows 10 ARM) than on Mac Pro 12 core 3GHz machine with same Parallels 17 and Win10 Intel... without getting hot or loud ;-)I’m interested to know what simulation software you are running.