You're confusing weight distribution with sway control - no such thing as "4-point antisway bar". Some weight distribution systems feature sway control as a function of the design of the system - Equal-i-zer, Blue Ox Sway Pro, etc - while other weight distribution systems require the use of a separate friction sway bar, or even 2 in the case of a large trailer. My suggestion is focus on learning more about exactly what it is your buying, and why. ;)
As an aside, you have too much trailer for your short wheelbase Nissan, especially if it's a V6. My own Coachmen Freedom Express is very similar in length and weight to your new Winnie and I wouldn't tow it with anything less than a V8 powered 1/2 ton truck. JMO so take it for what it's worth. :)