mono bnc = L+R sum?

when boucing a stereo out bus into a mono downmix, is l+r perfromed by default (thereby possibly increasing the modulation by ~6dB and causing clipping)? or is this to be set up somewhere? do you set up a proprietary mono out bus for mono bounces?

thank you.

actually, furthermore, what would be the exact relationship (gain staging-wise) of a project’s pan-law settings, and the resulting gain of a stereo bus bounced as ‘summed to mono’; and that compared to the same signal sent & rendered through a mono output bus…? thank you.