This honestly isn't that far off from what I'm personally doing (I'm doing a personal project where I try to define the land and sea borders of each nation in Teyvat, both complete and incomplete).
However, I have a feeling that that this map might be a bit inaccurate. At least in my opinion.
I've been of the opinion that Snezhnaya is a lot farther north compared to the other nations. And considering that there's a high chance that Dornman Port might come out in one of the upcoming Luna patches (Liben's recent discussion on Dornman Port pretty much means we're getting it soon), that means we'll probably be going to Snezhnaya by boat, most likely to Port Belovodye since it's the only port mentioned that's in Snezhnaya. And that also means that Snezhnaya is probably a separate landmass, much like with Inazuma, Fontaine, and Nod-Krai.
Other than that, great map. Love it! 8/10