Those are rubber grommets. They'll protect cables from wearing on metal that pass through the case.
Likely for things with hard wired controllers, like fan controllers or led lighting. You can hang the controller outside of the case in the back where nobody will see it.
As good as eating.
Most are like junk food Few are like fine dining And a few are like eating food you hate at a friend's house but you're trying to be polite.
Overall I'd recommend experiencing it, but if you don't or can't no biggy.