My goal is recording all the in game sounds via headphone via OBS (with in game audio style selected headphones as well) since headphones are better in quality than onboard sound...
I think there's a misunderstanding here on how audio works.
All the in-game audio you are hearing is stored as digital audio files on your PC. All your headphones are doing (assuming bluetooth) is taking that digital signal and converting it to analog for you to listen to. That's essentially what all soundcards do: Take a digital signal and convert it to analog.
What you are implying you want to do (and correct me if I'm misunderstanding this) is re-encode that analog signal back to digital. This is silly; not only does the actual process degrade audio quality, you need to remember that pretty much all gaming devices have trash input ports. You'd lose significant quality versus the existing digital files.
The files on your PC are already digital; youtube will convert them to whatever format it uses, and the quality of the conversion back to analog will be handled by the end-users audio equipment; you have no control over how good or bad that process is since its dependent on the users to convert the audio coming through youtube from digital back to analog again. The only thing you should worry about recording externally is your microphone input.