Some beers form more than others. Some yeast strains form significantly more than others. It happens with every beer. With your past batches, you still would have seen the ring hanging around the sides of the fermenter just above the surface of the beer.
As far as transferring, I rarely transfer anything. Fruit additions (or something in kind), lagering, oak, bugs, or long term storage, but that's it. I dry hop in primary. Some folks do like to transfer. A lot of us don't. Lots of debate on the subject on this forum. So yeah, I wouldn't transfer. Let it sit maybe 4 weeks (or at least a few days to a week after you reach your FG).
As far as kegging, I'm a bottler, so I can't help much, but from what I understand you're looking for either ball lock or pin lock cornelius soda kegs, not the commercial ones. Some are a little taller, some are shorter and wider, so it depends on the configuration of your keg fridge.