Yes, the "modern fat bike era" really started with the Pugsley in 2005 or so. I have a 2014 Pugsley and it's an interesting bike. Back in the day, they didn't have many hub options outside of the standard (at the time) 135mm hubs, so they used that on the Pugsley, front and rear. But how do you use a 135mm hub with a tire that's four inches wide? You offset it to the drive side for chain clearance. Yes the centerline of the hub does NOT align with the centerline of the tire. The tire is centered in the frame, but the seat stays and chain stays are offset to the drive side down hear the hub area. It's an interesting outside-the-box solution that has been obviated today with fat bike hub standards (which use a symmetrical wheel build, like most other bikes).

Many of Surly's bikes could be set up with any wheel size you desire, including "650b" / 27.5" / 584mm wheels. As long as they're disc brake wheels and you're using a disc brake frame, the rim diameter isn't of primary concern. There are secondary concerns, of course (like possible geometry changes, pedal strike clearance, etc.) if you go too far outside of the intended design envelope for the frame. The Bridge Club appears to be a super versatile bike -- perhaps one of the most versatile in the Surly lineup. There are some that are more road-oriented and some more trail-oriented, but the Bridge Club looks to be nearly as close to a do-it-all bike as you might hope to find. Surly correctly notes it can be run with a variety of wheel-and-tire sizes. I think the "650b" tire they recommend is a 2.4" tire (or 41mm if using "700c" / 622mm wheels).