Do I need rear LCAs for 1" drop on coilovers? Do I need adjustable toe arms?
 

I just got a set of HKS max iv SP coils and I wish to lower my car 1" to 1.5" (not sure yet). I also want to dial -2F & -1.5R camber in order to fit 17x9 +35 wheels coming in so they don't rub.

Question is, do I need rear LCA? Do I need rear toe arms to dial 0 toe all around or factory ones will do?

Bonus, are RS*R LCAs good for STX? thanks.

Yes (since you have targets you want to hit accurately and are considering autox usage)
No, and two aftermarket arms isn't legal for STX
Maybe, I'd have to measure the bushings to be sure, only use the factory hole positions, the non factory hole positions aren't STX legal.

If you're just doing local events for fun nobody should bother you, if you're top five at nationals someone might get their panties in a twist.

If you don't mind a bit more rear camber, you don't need LCAs, and you don't need adjustable toe arms either.

At -1.25" lower, my rear camber is around -2.7, which for me is fine for street and track duty. I'm running -3.4 up front with camber plates.

Your camber targets are on the low side if you're going to the track...

At ~1” lower, I was at -2.0/-2.2 degrees (L/R) at the rear. I didn’t see a need for LCAs since that was pretty much what I was aiming for.

Also agree with Dan above.

Depends on your car, some are worse than others. Mine, stock had almost a degree of cross camber which was fixed with LCAs.

Same, when I lowered by BRZ for the first time by 1", my rear camber was 1.5 degrees on the left and 2.3 on the right. I found this to be unacceptable so I bought the Whiteline rear arms.

If I could do it again I would do SPC, so I could get a cross-axis bushing instead of a poly bushing.