Use OBS as a webcam app is like using a modern battle Tank instead of a fly swatter. I'd expect with its significantly expanded capabilities to use more CPU. Sort of like observing/complaining that a Goldwing uses more gas than a moped??
Mind you, I'm just a user, not an OBS developer ...
With that said, on a i7-10700K, my CPU usage for OBS is single digit, so even double CPU usage is a non-issue, not to mention the default camera app doesn't have the functionality I require