Can you provide screenshot from Nvidia Experience?
Find War Thunder on the list, move mouse cursor on it, click details. Scroll down and check your settings for V-sync.
Also, go to Nvidia Control Panel. Click on 3D settings. Check if you do not have any FPS limit there. There are two limiters there - for active app and for "hidden window". Maybe there?
Try to use global settings.
PS. Do you have Aces.exe? I think you should use it, instead of launcher.exe. Sadly I am not using standalone client, so cannot check it (I play Steam version).
Try to remove WT profile from nvidia panel and use global settings. It's super strange that you have hard lock on 40fps. It's not refresh rate, strange number.
Well, you are doing pretty well trying to find the issue. Maybe check few more things before you spend time trying few more steps?
devtrackers.gg