KDE Plasma is generally less resource-intensive than Gnome, and has been for a number of years since it was optimized for low-power devices such as the original Pinebook and PinePhone (essentially low-end ARM SBCs, RPi3-class, in different boxes). VM performance may not be representative there.

Not that it's not a very valid use case to perform well in VMs, but that can be down to specific details of emulated drivers, etc. For example in a VM without good 3D acceleration Plasma can be run in software emulation of OpenGL -or- directly via CPU-based 2D rendering, and the latter is a lot speedier.