Hi,
First let me mention, that presets bundled with Forest Pack are "LWF ready", so there shouldn't be any gamma issue on commented set-up.
I'm afraid, that there are no "universal settings" as the final look depends mainly on the lightning set-up (in your case mainly on used HDRi map). Please double check if your scene is not slightly overexposed. The scene used for thumbnails renders has really simple set-up (similar to yours one): a
VRayLight (
Dome type) with a
VRayHDRI map loaded.
Feel free to get inspired by settings mentioned for example on
http://www.peterguthrie.net/blog/ or
http://bertrand-benoit.com/blog/, where you can find a lot of useful informations.
Attaching render of the "Common grass 01 (detail)" preset using the freely available "
BBB3 Vray Mat Scene" without changes.
To tweak the final look of the preset I would suggest you to add a
Color Correction map(s) and adjust it in a desired way.
Best regards,