If your audio is lagging, that's usually telltale signs of driver malfunctions.
Have you tried updating your audio drivers and making sure you don't have any extra audio outputs enabled that aren't being used?
Other than that, in OBS, you can change your audio settings to a lower bitrate. You do this by going to the "Output" tab in settings and switching it to advanced mode.
(I use OBS Studio. I'm not sure how it looks in original OBS.)
It lowers the quality and should help with the lag. The difference doesn't become obvious unless you lower it significantly.