Here's an extract from the current IL2GE ReadMe:
Requirements
OpenGL version 4.5 (
https://en.wikipedia.org/wiki/OpenGL#OpenGL_4.5)
IL-2 Selector (at least Version 3.4.2)
Settings:
OpenGL mode - DirectX is not supported
perfect mode
conf.ini:
[window]
StencilBits=8
[GLPROVIDER]
GL=Opengl32.dll
[Render_OpenGL]
HardwareShaders=1
Water=0
Current bugs/limitations and workarounds
artifacts with the default water textures in some modpacks
I recommend using Carsmaster's water mod to avoid artifacts (you may need to manually install it, even if it's included in a modpack you are using).
dynamic lights cause artifacts - I recommend disabling them in conf.ini:
[GLPROVIDER]
DynamicalLights=0
forests are flat (but using a parallax effect) (code for layered forests exists but needs performance improvement)
misplaced coast lines on some maps
no water reflections
no 3D waves
no cloud shadows
no shore waves / wave foam (code is there but currently disabled) - WIP
You need to set Water=0 in your conf.ini file and, at least for now, accept that no shore waves, wave foam or water reflections are available. It's also recommended to add Carmaster's water mod in lieu of setting Water=4.
Cheers