I run Lynx R fairings on my WRR and KTM 500 exc.
(a)
Weight. I don't have the weight of the Lynx vs stock equipment, but I'm planning a wiring project soon. When I take it off I'll try to remember to weigh them. My guess is that the stock shroud/light weight ~5lbs and the Lynx ~10 lbs.
(b)
Off road ST capability. Less. As referenced above, there is additional weight associated with the fairing which in and of itself is a hindrance. The weight is carried over the front wheel which doesn't affect the overall balance in any noticeable way (IMO), but the the added weight will require a small amount of additional force for steering inputs. I run steering dampers so I can barely tell. The biggest issue is actually just the size of the fairing; a lot of ST has branches and brush that whip across the front of the bike. The height of the fairing and the windscreen means more of this will be impacting the bike then your chest as opposed to just your chest
. It's size probably increases to odds of damage in certain get offs.
I've haven't run the TAT, but I do a lot of that kind of riding and would definitely recommend it despite the above-referenced trade offs. The light output is insane. Having the wind off my chest ups the comfort level dramatically. The blank-slate dash is great for customizing switchgear, GPS and power outlets.