I booked without free at sea on my prior sailing. About a month out, the price dropped for a slightly upgraded cabin with the drink package. Norwegian will gladly let you upgrade your room, as long as the upgrade costs money.
For example, if my original booking was $2000 (no drinks), and an upgraded cabin with drinks costs more than $2000, I can pay to upgrade and get the drinks package.
As long as you don't need to book a certain type of cabin, like an aft balcony, then I recommend getting the cheapest cabin you can get and keep an eye on prices. Chances are they will drop as they try to fill up the ship last minute. (At least for sailings in 2022). You might get those drinks for a lot cheaper.