NCL offers these kinds of promos basically all the time, it's not as great as it might sound lol. The 30% off is off of some inflated rate that I don't think anybody pays. Drinks package, you have to pay about $22 in gratuities per person per day. If you take it, the first 2 people in the cabin have to take it (can't just do it for 1). The specialty dining, you get 3 for 7 days cruises and 4 for the 11 day I'm doing. Gratuity is $23/person (total not per day) for the 4 restaurant package. Only the first 2 people in the cabin get it. Though last time, the kids were able to order off of the kids menu (same menu as at the main dining rooms). The "free excursions" is only $50 off for the first passenger, you can use it once per port. We had this last time and didn't even use it since ship excursions are so overpriced. I think it would only be useful if there was some special excursion that you had to go through the ship.
I did a Cruise Compete quote. Ended up being about 12% off of the base fare for first 2 passengers (kids was some small discount). $150 OBC that wasn't on the quote was a nice surprise. Plus the Amex plat perks. All stacks!
Fully refundable. If price drops, you can ask for a refare. They're offering free air for the second passenger now. So I find usually that means they inflate the price some. So it might go down. But then new ship, so maybe not. We didn't take the free air since you can't control the flight times and can only stay 1 or 2 nights pre and post cruise.
ETA: The Amex plat perk doesn't work on the sailaway rate and might not work on group rates. My parents' cabin was going to be a group rate for a slightly better price, but then the TA ended up switching to the regular rate since it worked out better. I think you do have to pay the deposit with a plat. Feels like it works the same as FHR - pay deposit with plat, then can pay rest with any Amex.