Note: Elgato has a great new capture device called 4K S. The name is similar to the 4K60 S+, but they are very different products. Find out more about the 4K S here.
Elgato Game Capture 4K60 S+ has full support for Windows 10.
Elgato Game Capture 4K60 S+ cannot be connected to a Mac - it does not directly support macOS.
That said, you can record on the SD card, and then mount that card separately onto your Mac to access the footage for editing or uploading.
Windows Software From Elgato
Elgato Game Capture 4K60 S+ can use Elgato 4K Capture Utility v1.7 and above for Windows 10.
Elgato Game Capture 4K60 S+ cannot use Elgato Game Capture HD Software for Windows 10 at all.