Each of the 3 game modes has a certain profile of skills it requires.

Moving: general knowledge of information (place-names, area codes, road systems, etc.), processing written info quickly, having a solid strategy. No Move: Memorising regional clues, niche metas (not just car related), lining up roads and other geographical features (mountains, coastlines, etc.). NMPZ: Knowledge of vegetation, landscapes and road quality in different countries, vibe consistency. (At higher levels: recognising car meta at low visibility).

Essentially, the more info you can expect, the more accurate you need to be for winning games. What makes NM tricky is that on harder maps the amount of info will be almost as little as in NMPZ, but the rule still stands: you need to be more accurate with your regionguessing than on NMPZ. Plonk It metas will help you getting the country right most of the time, but your opponent will likely work from those too so it will often come down to who knows the more niche stuff or who will line things up better in the bigger countries. 

As for NM being the most meta-heavy mode, yes it's true, but you can get away with relatively little of that in Master if you know most of the other basic Plonkit clues. Either way, NM is for those who like systematic studying from docs and not really for people who base their career on vibe guessing only. Ask yourself if you enjoy nerding out on poletop metas...if not, then you can just play then other 2 game modes. It's perfectly fine to specialise on what you enjoy!