Yes, thats right, the game starts off in a smaller resolution window box, after I select Civ and start game, the in-game options change the resolution as I mentioned in the above post.

Do you know how can I change the resolution of the game at start ? I wanted to launch locally (outside of voobly) to see if I can change that, But I am unable to figure out which exe Voobly is using to launch it.

The resolution of the main menu never changes. At least I haven't found someone that has done it.

As for the offline launch of the mod, it doesn't work straightforward. It requires modifing some files and I'm not familiar with the process.