I would ass that the basic shape of the sohc lends itself to cafe looks better than the dohc does. However, the 77/78 have different tanks, so take that into consideration.
I do have to say I like the sohc rear drum. It works very well with good feel. I do not have issues with the front squealing though. I used a few tricks that work for me. Slotted the pad, chamferred the sides of the pad, make sure the plastic ring is between the piston and pad. I rarely have any squeal now. On a rare occasion, but I get it with my 06 yamaha every so often too. A very high temp grease can be used on the sides of the metal part of the pad, that slides between the rubber seal. High temp as in it keeps its shape at like 500+ F, so it does not run. Pad composition makes a difference, too.
Mileage, as Shiny says, it depends. However, a maintained CB can hit 100,000 miles(160,000K) before major work. However, you are also looking at age. Age makes gaskets and seals fail. So, if the engine has never had those replaced, good chance you will be doing it in the near future. Doesn't mean there is a problem though.
The ride IS the adventure. The destination is just to get gas!