This may be a bug with the new update: there appears to be no difference between “Ambiance” & “None” when setting the edge peek background. The “none” option works well when using one of the letterbox settings in a dark game like Thief & while I can change the setting in the vorpx menu, the change does not take effect.
There has been a change in regard to how that is handled: what happens now is that EdgePeek always uses the “Ambience” background, while the normal gaming background is switchable between “None” and “Ambience”. If “None” is selected as background, the ambience backgrounds fades in when activating EdgePeek and back to black when leaving EdgePeek.
All things considered that makes more sense to me than the prior behavior.