For other analog-emulated plugins, some use -18dBFS or -20dBFS as the reference level, corresponding to 0dBVU on the VU meter. I believe Slate VCC uses -18dBFS.

Is X2 Console Emulator's VU meters calibrated that way? What level is it when the VU shows 0dBVU?

This is important when working with multiple plugins from different developers.

the rms varies on the material its self, i.e an overdriven guitar will have a higher rms value, than say a cello, even tho they both peak at the same level, you know wat am saying, i dont think the CE is calibrated in anyway for mixing ref level, just has a setting for the two different values, like in the track meters

I don't really care for the peak value though. Since it's a VU meter there (whether it reacts like a real VU meter is another story) I expect it to give me a rough estimate of loudness, and in a way roughly corresponds with the RMS level. Slate Digital VCC, for example, would read roughly around 0dBVU when fed with a stable signal of roughly -18dB RMS.

For proper gain staging, I think it's essential to know which nominal level the VU meter and the Console Emulator itself are calibrated at.