Hard candies in the store shows $2.99 lbs. But the candies are of different types. Can I just pack them in one polybag and get them weiged at the mentioned rate? Or, do I need to keep them in separate polybag while checking out?

You can mix them up

Pretty sure you can mix them up. I think they're all by the frozen section I'm not mistaken

No, they are all the same price. You can put all your choices in one bag, or separate if you plan to use them seperate.

You can mix them if they are all the same price

Keep separate.