The Bushnell would be a minimum for an 80mm scope, but it will get you by. A 128RC or 701 is a much heavier head and a much better choice for that size scope. The 701 gets you spring loaded handle action and a short balance plate - more a plus for video use than for spotting scope use,to be honest.
No difference in smoothness. Just means the handle gets a little power boost from a spring when you return it to level. Steadiness and payload is the same.
Only difference is leg height. The 190 is the shorter of the two. Stability is the same. If you are 6 ft or better, go with the 055. Always better to get your height from the legs, rather than extending the center column, when it comes to stablity. Going carbon reduces weight slightly, but improves dampening, but you pay dearly to get it. Only place to go up from Bogen is Gitzo, but that is much more expensive. Bogen has been the standard for spotting scope tripods, forever. Can't go wrong with Bogen.