I prefer the aluminum -5 chassis on both carpet and clay surface . If you need more steering simply add the brass weight under the servo, and or the brass esc plate. It will help keep the nose down.
The Stock Spec buggy is very light out of the box to reach minimum weight for 2wd class of 1499g. Some strive to be on the 1500g mark, some prefer heavier wet weights.
As for slipper lockout or slipper, its a preference.