> Should NEIPA/NEPA be in 21 or 18? Based on bitterness, it would fit more in line with an American Pale Ale.
IMO neither. I find the majority of NE / hazy "IPAs" to be nowhere near bitter enough to label as IPA, and they're typically less bitter than an APA too. To me they represent an entirely new (albeit derivative) style creation of modern American craft brewers, and should be named as such.
The originators of the style, most notably Heady Topper, are far more bitter than what typifies the style today.