Hi a22ymee, and welcome to cruise-chat.
I was on Regal Empress years ago, before she was operated by Imperial Majesty. She remains among my favorite ships. But, I need to caution you that this will be an entirely different experience than Carnival. Your cabin will almost definitely be smaller. There were no toiletries provided in the bathroom (other than a bar of soap) -- unless they've been added in the last couple of years. Same goes for hair dryer. Although the cabins are small, there is good storage space, particularly as she is currently offering 2-night cruises.
No irons allowed in the cabins, and no public laundry facilities that I recall. Hopefully, someone who has been onboard more recently than I will stop by and answer your other questions (although I have a strong suspicion that a suit will not be needed for dinner).