Is this game considered canon or a spinoff like Brotherhood of Steel or semi-spinoff like Tactics?

I'm sure it's just a spin off. But it looks fun at least, can't play it since it's not on my Phone type.

It's meant to be fun. (we hope you think so). You can number your Vault any # you want -- whether it's a Vault that exists in Fallout lore or not.

For the response. Apart from vault number though, how about other things in the game like the things in the vault?

Yes, it's canon. everything you found in the game like the tings in the vault are all canon. It will appear in the main game. Trust me, it is.

difficult to answer. the game has as afaik no actual "story" apart from random events (raiders, fire etc) that happen. The different items/dwellers that you can collect are from the fallout games, partly "named" items or characters that do appear in the previous canonic games.

That said, you can assemble a collection of characters and items in a vault that you name for example "Vault 101" that never actually appeared in said vault in the game, so the result is a completely stupid impossible setup of characters/items that never occured in any game. and as the layout is in 2 dimensions, it can never be accurate to the actual vault that appeared in the games.

So story isn't canon but atmosphere is, is this the case?