If you’re really into video encoding and streaming, then YouTube can give you much more technical information about clips when you’re watching them in the mobile apps. Tap your profile picture on the Home tab (top right), then choose Settings and General and turn on the Enable stats for nerds (Android) or Stats for nerds (iOS) toggle switch.
To see said stats for nerds, tap on a video, tap the three dots in the corner, and then choose Stats for nerds to bring up the overlay while the clip plays underneath. The information displayed on screen in real time includes the resolution of the clip, the audio and video codecs used, and the amount of bandwidth you’re using up by streaming it.