So again this is for the race car. I have HICAS lockout, toe adjustment of course, and adjustable upper control arms (possibly Tune Agent, they're blue lol). Rest is factory (except the coilovers). I'm planning to run about 1mm toe in per side, and around 2-3 degrees negative camber. Do I need adjustable traction arms as well?
Unless you're very lucky and your specs put them in a good spot, yes, the traction arm runs off axis so camber and toe both feed into/off it and you'll probably have weird wheel behaviour through it's travel.
Yeah I can see where it sits in the overall geometry, it's length affects both toe and camber. I was thinking with such mild settings I might not need it, might be enough give in the rubber bushes.
