Playing Black Mesa with a ‘normal’ monitor FOV currently messes up the image due the DirectVR weapon handling, which moves the weapon out of sight in VR mode. At lower-than-VR-FOV it currently totally messes up the image though. Has been taken care of for the next build already, for now please switch to ‘Generic HMD’ temporarily and turn off automatic weapon handling on the DirectVR page of the menu. Then switch back to ‘Generic 3D Display’.
That aside:
Like the message that gets displayed on each launch in SBS3D mode says, vorpX is made for VR primarily. SBS 3D was added on request and is not officially supoprted. Any potential expert settings are purely VR related, there aren’t any expert settingd for SBS 3D mode.