So I did a test using GPU Watch active and noticed when running the YouTube app it uses Vulkan as the API. I ran a 4K 60FPS HDR video at fixed 2160p settings. It shows around 10 to 20% CPU usage with a few spikes above 30% (probably when caching) and 0 to 2% GPU usage. I decided to run the same video test again using YouTube in Chrome instead and GPU Watch shows N/A for the API used. The CPU usage numbers were about the same but the GPU usage was floating around 20%. The odd thing is, the YouTube app made my phone warm up whereas in Chrome it did not.