Pretty much so. It depends if the source is mono or stereo. With Mono, both sides get the same signal, with stereo it is what it is when pan is centered. So yes, ctrl/click sets any control to its default value (pan, volume etc), and with the fader set to 0 dB this way, meter readout should show the actual input. This becomes red when 0 dB is reached or exceeded. It is not super accurate because it is beeing transmitted with limited time precision.
Note that hardware inputs are limited to 0 dB anyway, some even limit to less; you shouldn’t make it too hot, with 24 bits recording depth (that’s a mere 144 dB) you can well afford to give some 9-12 dB or so headroom - but you knew that already 
If you record multiple channels, the record cues determine realtime stereo recording mix. As said before, with the PRO version, raw input signals are beeing recorded on the performers’ computer regardless of any level controls (except inserts when enabled for recording).
Finally, looked it up again and I was wrong regarding the pan action: when centered, both channels are at 0 dB and not attenuated at all, and you can prevent clipping by having Performer set hardware input gain such that no meter moves too close to the top.