Is the TX on a ASUS AC3200 2x2 or 3x3 ?

I am transferring from a AC68R to a AC3200. On 5 GHz, my AC devices from the same location could easily connect at 1300/1300 (TX, RX). However on the 3200 the max I can active is 526.5/1300(TX, RX). I am wondering if this is a firmware issue or a hardware limitation. I am currently running ASUS firmware 3.0.0.4.378_9313. I am curious if anyone else has observed a similar behavior. And if anyone has achieved the full 1300 TX/RX link speeds.

I contacted ASUS and they gave me the usual...

Is the TX on a ASUS AC3200 2x2 or 3x3 ?