The Royal Caribbean website is often held up as an example of poor design and non-answers. For example, under their FAQ for gratuities you find a dozen or more answers about the automatic gratuities but never a mention of how much they charge. They charge $12 per person/per day. $14.25 per day if you are in a Grand Suite or higher level suite.
The $65 drink package covers a lot of beverages, but bear in mind they are really just adding specialty coffees and tea (not sure what specialty tea is) to the $55 package. So, if you are more concerned with alcohol and sodas then the $55 package would make more sense. It is surprisingly easy to rack up $55 a day (and by the way, that amount includes the 15% bar tip), without really drinking that much. A 16 ounce beer (Royal sells most beers in 16 ounce aluminum bottles) costs $6.64 with the tip. A mixed drink is anywhere from $6 to $10. A glass of wine is around $8 to $10. Bear in mind the packages do not include all liquors, wines, or beers. The limit is also at the $10 mark but you only get charged for the amount over the $10 limit. Unlike Carnival, Royal Caribbean has no daily maximum number of drinks you can get with a package. Here's a hint: either buy the package online before the cruise, or wait until the ship leaves New Jersey and is in international waters. If you buy it on the ship while in Cape Liberty they will have to charge NJ sales tax. In summary, to answer your question, you'd probably need to have at least 6 to 8 alcoholic drinks per day to get your money's worth. Again, it depends on what you drink. Most people are better off just ordering per drink and not bothering with the packages.
Explorer does not have all the specialty restaurants found on other Royal ships. It has Portofino's and Johnny Rockets hamburgers. Explorer goes into the shipyard for upgrades this fall, where many new places will be added. The dining room and Windjammer are fine though.
I think you will find Carnival and Royal Caribbean are very similar in most areas.