When watching youtube videos of fatbiking, pay VERY close attention to what substrate they're riding on. Yes the tires float...somewhat. But traction is everything. 3 inches of fresh powder over hardpack? Yes. 6 inches of fresh snow, probably not. Mainly because snow is a loose substance until it gets packed. Imagine 6 inches of loose dirt or sand. Same same. The tire MUST be able to reach something that it can bite into. Regardless of width or tire pressure, though these things do have an effect.

I have a fatbike. It's a LOT of work. My personal decision on the utility of it is up in the air right now.