:like:

I'm very happy with this addon it gives me what I need on youtube (slow/fast speed, default *4K, HD).
I wish this kind of add-on can be added on android ;) (mmh maybe it can)

*Sometimes, it doesn't shows the 4K as default (why?).

This addon is very helpfull but it has some bugs - it spams many same elements (style and script - including usermade) into head of document. It can make browser slower as well as it takes more memory.

I love all the little adjustments the extension allows, as well as the customisation, which is a very nice aspect that YouTube itself doesn't seem to care much for. However, there seems to be a conflict with the Remove Youtube Suggestions extension which causes it to not work, so I'm forced to keep it turned off :/
I hope the conflict is fixed soon, so I can go back to using this.