In the Advanced section of the Reflector 4 Preferences menu, there are 3 settings for what protocol a device can connect to Reflector 4 for mirroring.
The 3 protocols that are accepted by Reflector 4 are AirPlay, Google Cast, and Miracast.
Reflector 4 will automatically detect the protocols that are compatible with Reflector 4 on the Mac and Windows PC and enable or disable those settings accordingly. If you see that the Miracast setting is greyed out in this menu, then that would indicate the Windows PC does not support Miracast.
Note: macOS is not compatible with Miracast