MCM Compatible (but not required) tooltip delay configuration. Game defaults to 0.5s.
The game redraws the tooltip every time you move your mouse, so the delay cannot be 0 or it looks glitchy (it's annoying anyway).

If you don't have MCM, a config file will be created in

C:\Users\[yourName]\AppData\Roaming\Road to Vostok\FastTooltip.cfg

Tested on EA Release build with metro's mod loader.
Thanks to everyone in the RTV discord modding channel for their help!