A system should have all updates categorized as "critical" installed.
Updates classified as "optional" are...well, up to the user, not necessary for Windows operation.
As to whether one enables automatic updates or not...personal preference. I prefer to manually go to the Windows Update Site and then choose the updates I want to install, since auto updates has been known to sometimes install items which are not critical.
FWIW: I suggest that you NOT download drivers for your system components from the WUS. IMO, it's smarter to get those from either the website of the system manufacturer or the website of the motherboard/other component manufacturer.
Another FWIW: I don't believe in updating drivers unless I have a problem with that component. I try not to "fix" things which are working well