For graphics: dgVoodoo 2.54 (http://dege.freeweb.hu/dgVoodoo2/dgVoodoo2/); put x86 version of D3D8.dll in the game folder.
For audio: DSOAL latest (http://vaporeon.io/hosted/dsoal-builds/); put all 3 files in the game folder.
So this is just something to answer myself, but also other players still trying to figure out how to get GR working on Windows 10 with great graphics and audio.
1. The original installation for GR has DRM included. You can go to GOG to grab a copy of DRM-free Ghost Recon. In you don't want to buy this one but have the original installation media there are instructions available on this forum to get it working like that as well.
2. Graphics. The bloom effect mod from ENB series seems to not natively do 32-bit Z-buffer. It looks a little that the option doesn't get exposed properly. No worries, since there is something called dgVoodoo2 that actually is capable of exposing this option properly so you can set it in-game.
Grab a copy (I get best results with version 2.54, upwards rendering goes bad for me), place the correct DirectX file (D3D8.dll) in the game folder and configure dgVoodoo control panel application as needed. After in GR you should now be able to set 32-bit Z-buffer in the game options screen. Using this for AMD graphics cards owners that update their drivers also resolves that annoying MiniDumpWriteDump error for the atiumdag.dll file.
3. Audio. Get DSOAL and place the 3 files in the game folder. This should enable EAX while not even owning a soundblaster card. You might need to do some configurations to activate in the game options screen.
Have fun. Maybe this should be made a sticky topic.