Would "rising in thunderheads of tobacco smoke" be an example of personification or a metaphor?
The quote in the question is an example of a metaphor. A metaphor is a comparison of two unlike things and does not use the words "like" or "as." In this case, the quote being used is describing the smoke that is surrounding Captain Beatty. The smoke isn't thin wisps of tobacco smoke. It's as thick as the biggest and most dangerous storm clouds.
Captain Beatty there, rising in thunderheads of tobacco smoke.
The comparison being made portrays Captain Beatty and his movements as similar to a big, powerful storm cloud. He is imposing and dangerous looking. Because the quote says that Beatty is in the cloud, I picture Beatty as enshrouded by the cloud. The line gives Captain Beatty a sort of Satanic presence, which is exactly the kind of person that he is. He is the ruthless, malicious, shrewd, and destructive antagonist of the story. At times he comes across as friendly and soft, but that is only to gain an advantage over some other person.