A true Super35 kit from Superior Axle has no spool option and to the best of my knowledge, there are no 30 spline spools made for the Dana 35c axle... the Super 35 from Superior Axle converts your 27 spline axle shafts to 30 spline axle shafts. There are some "fake" Super 35 kits not from Superior Axle that use 27 spline axle shafts but they're not worth the $$$ to install.
You have a choice of lockers including the Detroit Locker, ARB Air Locker, and the Eaton E-Locker with maybe another locker or two like the Ox Locker as well.
With probably 110K miles on my Detroit Locker, I love it on the street and of course on the trail. No one riding with me on the street could even tell I have a Detroit Locker installed, it is well behaved after you learn to drive it. It is "self-teaching" so within a week or two, you'll have learned without even thinking about it how to drive it so you don't get the clunks and bangs you may have heard about.
The only conditions I wouldn't want to drive a Detroit Locker on would be ice or snow covered roads where it could be a handful if you weren't extra careful. It could be a handful on a sloping ice covered trail too. But if you don't drive/wheel on ice, then it's a great locker.