for guidance on cruise docs. Actually you need to check in on-line at the RCI website, which you can do with a link at the bottom of the webpage I provided above. When you check in on-line, you will be able to print a Set Sail Pass which is all you need to have with you at the pier (well, your ID and method of payment for the shipboard account too). You just present the Set Sail pass, your ID, and payment method (credit card for most) to the agent. No need for a big booklet of cruise documents. Many don't even issue hard copy docs anymore, just going with e-docs. However the RCI hard copy docs will have luggage tags in them.
You can also get luggage tags from the porters when you arrive at the pier. They won't take your luggage without a tag on it.
RCI just says "a reasonable amount" of luggage may be brought aboard. Most people overpack and never use half the stuff they bring. It is just a few days after all. Unless you are in a suite, the cabins on the Majesty Of The Seas are not very spacious. Closet and drawer space is not conducive to large amounts of clothing.