In the analog/tape world, you always tried to keep the signal as hot as possible to get the best signal-to-noise ratio. And a little analog clipping was actually a bonus. The digital domain is the opposite. With 24-bit A2D and D2A, you don’t need to worry too much about the noise floor and digital converters don’t introduce noise as tape did. However, digital clipping is something that is to be avoided at all costs. There is almost no such thing as good digital clipping (bit-crusher might be the exception if you’re into that sound). So being conservative on the input level isn’t really an issue. Better to be a little lower and avoid any digital clipping than to focus on driving as hard as you can.
QC inputs set at 0dB will pretty much take a Humbucker pickup flat out without any issue. So unless you have unusually weak or strong active pickups, I’d set input to 0dB and not worry too much about it.