The quite popular Logitech C920 webcam used to natively support H.264, but they dropped it in a model revision a while ago, because "nearly every computer offered in the market features a chipset that can efficiently encode high definition video at 1080p" [1].

I've used that very camera (without the accelerator) on an RPi 4 myself, and the only way to get acceptable quality was by using the Pi's H.264 hardware encoder.

[1] https://www.logitech.com/en-us/video-collaboration/resources...