I too have a mouse pointer Flicker problem, currently using the latest Trial Version together with MacOS Mojave. When I perform a action in "Windows 10" I get a mouse flicker at times, It seems to transition from the "Windows" mouse pointer to the MacOS mouse pointer, and then back again to the "Windows" mouse pointer. This happens rapidly and is almost no visible. It appears as a flicker. I have found a workaround, by disabling all Integration with the MacOS, especially creating "ICONS" in the MacOS "Dock", it seems as if the "Dock" in mackOS gets Focus and then reverts back to the Guest OS. This fixed it for me, and because of this I am yet to decide, Parallels or the other one. I can't decide yet.
I was able to resolve this issue by going to View>Retina Resolution and switching from "Best for Retina Display" to "Scaled".
I finally found what triggered it for me. Whenever I used the screen zoom, even just the slightest amount, and even if fully restored to original position, cursor would flicker like crazy when switching to parallels VM for about 2-3 seconds. It would persist for the entire session until a complete computer reboot. Was able to reliably repeat these results. Given that someone has posted success regarding AutoCAD settings, and someone else with Display settings, clearly it's to do with scaling. Thankfully, ever since installing Catalina developer seed 8, the problem has disappeared. I can zoom and scale all I like now and my cursor switches straight away. Have not updated Parallels throughout this whole thing.