Class G = See and Avoid principle, no matter what service you are getting.
Yes the rules say that you can be in thick IMC flying IFR under a Traffic Service or even a Basic Service, doesn't mean it's a good idea.
If you plan a flight OCAS understand that it is ultimately YOU that is responsible for avoiding collisions irrespective of any radar service you are in receipt of. If you are uncomfortable with that, either don't fly or file a flight plan inside CAS or at least a Class F route.