Thanks to Delores: A Thmbleweed Park MIni-Adventure, now we know that the coroner and the sheriff (and I guess you could extend this to the hotel manager) are not the same person, as they are finally seen together in the same room.

I am still not convinced that they are human though. I think the story was initially gravitating towards the reveal that Chuck was replacing the inhabitants of Thimbleweed Park with robot-a-renos, as hinted by his diary and the humanoid robotic heads mass-produced at the factory, only to be eventually changed to the ending we all know and love/hate.