2D global Map resolution scale

Greetings,
I would like to create global map where You could travel between locations.
Something similar to Battle Brothers game.

Or this

There is not many information or tutorials about that kind of projects.
So if someone know at least what resolution of background should be, that would be great.

It’s going to be very small, as you can see. I’d say you could probably go with the minimum landcape size:

or any other minimal size from:

I’m talking about representing just the part you see here. Obviously as you move across the terrain you’ll need to stream other components, and might need to get into world composition:

That was very helpfull, thanks for your advice.

Right now, I’am making global map in PixelArt style.
The fine resolution for seamless texture is 128x128.
For Tree is 50x80 and 140x90 for mountain sprites.

That’s a bit old screenshot, right now everthing looks much better.