I'm trying to get my first T-Rex 450 flying and I have a 9XR Pro radio with the latest ER9X firmware.
I have a Redcom CM703 DSMX receiver and its binding just fine but I'm not understanding the relationship between how I setup the mixing in the radio and how the channels are labeled on the receiver ...I followed a mixing guide that said to plug my stuff in AETR order but my receiver is labeled TAER. I've tried to plug them in both ways and the rudder and throttle servo seem to work ok but the pitch is off and the elev and ailr are all wonky.

Can anyone show me a heli mix setup on a Turnigy 9XR with ERSKY9x (ER9X) using a spektrum/spektrum clone Rx? Thanks.

Flybarless or flybar?

Most flybarless controllers dont need any CCPM mixing in the Tx because it's all done in the flybarless controller itself.
If flybar then you need to set up a CCPM mix in the Tx, which is 3 servos @120 degrees for the Trex 450 but I've no idea how to do that in Open Tx software. Open Tx is notoriously difficult to program for CCPM helis so probably best head over to the open Tx forums and setup guides. A PHD in computer programming and a great deal of patience will help.

The AETR vs. TAER confusion is because Spektrum standard channel assignment is TAER so that's what is marked on the Spektrum compatible receiver..... but your 9XR uses Futaba channel assignment with is AERT. AERT is how it will work unless you change channel assignment in the Tx.