Under speaker settings, HQPallows you to set speaker distances. The manual only mentions setting speaker distances when doing multichannel. So, do speaker distances do not matter when doing 2 channel?
The speaker settings can be used for stereo balance. Multichannel in this context means two or more. Whether it matters or not with stereo depends on the shape of your room and the configuration of your speakers and listening position. If you can’t place the speakers symmetrically then this tool could help.