Unless the store was on fire, or someone died, I wouldn't say a single thing to the manager while he is on vacation. Let him enjoy his time away, and he will appreciate YOU doing his job in his absence. When he comes back, have an opportunity to speak to him briefly and fill him in on the high lights. Throw in, "I understood a lot more of your job trials now" and laugh it off. Save the detailed report for your own file. Otherwise, you look like a tattle tail, and that you need to be micromanaged.

If the guy already knows the other guy is wonky...find the way to make yourself shine: by doing your job, and his, and being a good sport about it all.

And, really, I would ignore the guy as much as humanly possible. Wearing a polo shirt instead of a shirt/tie might be off limits...but, no reaction would ever come from me. If he wants to disobey "rules" (and I happen to think dress code rules are silly), let him. Mention it once, and move on. Mention it to the 'boss' and let him do what he thinks appropriate.

I would ignore him completely, in regards to the silly stuff.