In railway station signboards in India, the normal practice is to have the state language at the top, followed by Hindi (unless it is the state language), followed by English.
(However, in Pakistan Urdu is always at the top even when the state language is different (as in Sind and Khyber-Pakhtunwa).
There are some states where the script of the state language is Roman script, even if the state language is not English.
This seems to prove that the station is in Arunachal and not Assam. And the present signs all say “Bhaluk Pong” instead of a single word.
Note that according to the convention mentioned above, Naharlagun should have had the English script at the top.
Now to Meghalaya:
This is the only station presently open in Meghalaya. It is adjacent to Nolbari:
You can see that this is in Assam.
Now to Mizoram. This is the only station presently open:
There are a few stations in Nagaland. the best known is:
Also in Nagaland:
There are or were other stations in Nagaland. Naginimora was closed long ago. Tuli did have the branch from Amguri converted to BG, but there are no passenger services.
Tripura has Bengali, and Manipur has something else in Meitei script.