I'm running the following:
Mord's immersive American voices (this is a must have, IMO)
Bil's improved rank and branch insignia
Bil's gridded terrain (another must have)
Rambler's high-vis minimal base markers
No explosions background sounds (No more listening to my wife complain about the constant thudding).
Both of Vein's muzzle flash mods
Vein's explosions and smoke (the explosions are overdone, but better than stock. The smoke is a big improvement)
Vein's flames mod (way too orange but, again, better than the stock graphics).
The two that I noted are definitely must haves. Mord's sound mod makes the game SO much more enjoyable. Gridded terrain makes it tons easier to see the lay of the land without getting down to level 1 or 2, but it doesn't look as nice in screenshots, of course. The rest are just gravy. I'd really like to see high-vis action spot highlighting and some toned down flames, but otherwise I'm pretty satisfied. There are some really nice UI mods that change the gun vehicle silhouettes, but I kinda like the simple black outlines.