Not sure what ETF stands for?
I know maratsade already explained what it means, but it stands for Early Termination Fee.
Here's the link to the terms of the ETF.
With regard to Youtube, it can be somewhat problematic for me in the thick of the evening digital rush (~7PM EST - ~11PM EST), but outside of that it tends to be okay, for the most part. I usually keep it to 480p or under in order to increase the chance of it working well and save data.