laurker Having messed around with TLP settings and CPU governors on an Intel-only laptop, I began to suspect the real culprits were budgie-panel and especially budgie-wm. They consistently demand more CPU than the equivalent components of lightweight DEs like XFCE (tested Zorin OS Lite 16.04), even when idling. I haven't tested other Solus MATE or Plasma to see how they fare in comparison.
You might want to take a look at the Gnome system monitor. I've noticed that with htop, budgie-wm is typically around 5-10%, but when I look at CPU usage with Gnome system monitor running, CPU usage across all the cores fluctuates from 30-50% utilization.