Real time: Real-time backup means that files are backed up whenever they change, usually upon creation or save. It’s also called mirroring and is handy for keeping an immediately available copy of rapidly changing data sets. For less volatile data sets, the payoff doesn’t compensate for the drain on system resources. Instead, scheduling should be used.
The next page will show a list of all Google products associated with your account whose data can be backed up. All of them will be selected by default, so make sure to unselect all and select only youtube. An easy way would be to untick the "Select All" button at the top which will unselect all items. Then scroll down and check the "YouTube" option.