Mixing Win and OSX devices in a single group

If I am patching the same applications on the same schedule for Win and Mac devices, is there any need to separate them into two separate Groups?

Similarly, if I have mixed Win and Mac devices into a single group and apply Windows and OSX worklets to run on the group, will Automox be smart enough to only run the Window worklets on Windows Devices and OSX worklets on OSX devices?

Yep that’s correct. You can mix and match in the groups and the policies attached to those groups will run on the relevant OSes.