Do NOT put Win10 Insider Preview on your only phone! Just wait until it's either released or MS says it's supported. What's the big rush? If you brick your phone it's going to be your fault. Nobody to blame but yourself.
Just sit tight and wait for the official word. Some stupid HTC Chat support rep doesn't know diddly-squat about what's going on.
If your HTC 8x is your secondary phone that you don't care about, then fine.. go ahead and hack the crap out of it but from what I've read it's not. Just wait.