It will delete {count, plural, =1 {1 video} other {<x id="count"/> videos}} uploaded in this channel, and you will not be able to create another channel or account with the same name (<x id="PH" equiv-text="videoChannel.name"/>)!
The video quota only takes into account the size of <x id="START_TAG_STRONG" ctype="x-strong" equiv-text="<strong>"/>uploaded<x id="CLOSE_TAG_STRONG" ctype="x-strong" equiv-text="</strong>"/> videos, not transcoded files or user export archives (which may contain video files).