So, not a WRX, but I've played around with both the VSC and TC modes quite a bit in my BRZ. It's a tail-happy car (which I like), so rather than go full VSC/TC-off, I simply use VSC sport mode. It introduces more delay into when the nannies step in and try to save your hash in a slide, but doesn't really turn them off. Though I associate wheelspin with TC, it seems like VSC sport also allows a bit more of that.
Actually turning TC completely off in this car is quite a dance, a sequence of things you do right after turning on the car.
I have a 13 STi , I turn mine off in the rain , it's fun to slide it around corners . But also when driving the canyons around where I live , the TCS can slow you down a little . I still haven't figured out that center diff control yet ...any advise ?
I turn my traction control off and engage launch control at the strip. I turn traction control off, but leave Stabilitrak on at the track. The stock suspension is tuned to understeer just a bit. However, you can induce oversteer pretty quickly. I set the MRC to "Track" mode at either venue.