Smoking in public buildings is illegal in Nevada except for casinos, bars/clubs with no food being served, strip clubs, and brothels. So there won't be any smoke in the rest of the hotel (except smoking rooms) unless people are being naughty. But the older properties are pretty much 100% casino, so there's smoke everywhere. I recommend Encore Tower Suites.
Do not prepay your hotel if you want a chance to get it comped. They can't undo prepaid rates. Using FHR rates should not be a problem as long is it is not prepaid. I'm not sure if you can get a Four Seasons room comped easily.