Yes, the stalks will eventually shrivel up and die. If your stalks are really big now, you could take one or two, but no more, it needs some energy now! Once the stalks are all dead, just tidy up the ones that are on the ground and leave the rest. I always heavily mulch around the crowns in winter, weed then stack around them manure, and in the spring they will come up wonderfully. I do this also with artichoke.
Mine have been badly drought affected this year, they have been quite poorly, but I did manage to get a baby crown from one of them going, so I will have a new2 year old rhubarb plant next year! Crumble here we come!
The cauliflower will still be edible even if the curds are coming apart but hurry up because it will flower otherwise. You can chop it up and freeze it if necessary, it will be fine for soups and gratins. I am envious, I have never managed to grow cauli.