Tuning Parallels' guest OS configuration options for best Mac performance assumes that you have guest OS applications that you wish to leave running at all times, and that you want them to have minimal impact on your use of your Mac. An example would be running Outlook in the guest OS, so you can frequently check your corporate email. You want your Mac applications to continue to run, without any big performance hit from running the virtual machine.
Memory Allocation
Set the guest OS to the minimum memory required for the OS plus the applications you wish to run. For basic Windows applications, such as email and browsers, 512 MB should be sufficient. This will leave more RAM for your Mac applications.
CPUs/Cores Allocation
Because guest OS performance isn't the goal here, setting the guest OS to have access to a single CPU/Core should be adequate to ensure that the guest OS can operate well, and that your Mac isn't unduly burdened.
Video RAM Allocation
Video RAM and its related setting actually have little impact on your Mac's performance. We suggest leaving it at the default setting for the guest OS.
Optimization Settings
Set the Performance setting to 'Faster Mac OS.' This will give preference to allocating physical memory to your Mac instead of dedicating it to the guest OS, and improve your Mac's performance. The downside is that the guest OS could be short on available memory, and perform slowly until your Mac makes memory available to it.
Turn the Enable Adaptive Hypervisor feature on to allow the CPUs/Cores on your Mac to be assigned to whichever application is currently in focus. This means that as long as the guest OS is in the background, it will have a lower priority than any Mac application you're running at the same time. When you switch focus to the guest OS, you will see an increase in performance while you're working with it.
The Tune Windows for Speed feature will automatically disable some Windows features that tend to slow down performance. These are mostly visual GUI elements, such as slow fading of windows and other effects. Overall, the Tune Windows for Speed settings won't have much effect on your Mac's performance, but should give the guest OS a nice boost when you're actively working with it.
Set Power to 'Longer Battery Life' to reduce the performance of the guest OS and extend the battery in a portable Mac. If you're not using a portable Mac, this setting won't really make much difference.
