The Ring sensors are standard Z-Wave and can be paired directly with Hubitat. I'm not familiar with DSC Power G.
It depends. Z-Wave devices can only be paired to a single hub. However, hubs can share information with each other directly or through a cloud service. There is a community Ring integration that I believe allows Hubitat to "see" the device states of the sensors connected to the Ring base station. Check it out to be sure.