I have Parallels 14.0.1 on a new Mac Mini 2018, 32 GB Ram, Host Mojave 10.14.2 with Guest Snow Leopard 10.6.8, 30" display 4K, setting on "scale" (and change makes no difference in performance of the guest OS X). Recent Toolbox is running. System and all applications of the Guest OSX 10.6.8 react very slow. Any movement, finder windows, app windows, objects in FreeHand or Indesign, everything moves staggering and slow. Not much I would know to do. Settings like CPU can only be viewed while VM is running, with a note that for changing it VM must be off. But when I shut down guest VM, there is no preferences any more for CPU and the like. Very strange.