The Elgato HD60S does not work on MacOS with OBS. You can only use their supplied software. If you want that content in OBS you'll need to window capture or display capture the Elgato software.
Elgato misleadingly advertises the HD60 as "compatible with OBS" and "compatible with MacOS" without specifying that you can do one or the other but not both.
Apparently the Camlink IS compatible but I have not tested myself.