Anyone know what this creaking sound could be? I’m thinking freehub, rear wheel hub or axle. Do I fix by just taking apart hub and regreasing?

I’ve had something similar before and it was hub body bearings being obliterated and on another occasion the cassette was just loose. See if the cassette is loose first if that hasn’t solved it. Take off the hub body and inspect the bearings inside depending on the hub its fairly simple to take off in my experience, just a bit more fiddly when you put it back on because of the pawls.