Vanilla is fine but by using sharper, higher resolution reproductions of the original textures can't be wrong. And the one thing I kept original was all enemy models, because I liked the way they look. Also custom high res space skybox (I would often just stop by a window to appreciate the view) It added a lot to immersion compared to vanilla skybox. I picked custom models that I liked for certain weapons. As far as I remember I used mostly or only mods that were faithful to lore or original textures to keep it as vanilla as possible just better (higher res). I'm a big fan of old school low poly graphics but when its fullHD and better textures it's absolutely brilliant in my opinion. But from my experience it was amazing moded. Its like 7-8 years ago so I can't remember list of mods.

When I first played SS2 I moded it before starting. The Shock Community Patch fixes a host of issues and adds dozens of small touches and enhancements that improve the experience. If you're going to install just one mod, install SCP. It fixes an odd issue with one of the enemies.

If you do install rebirth, I'd also suggest the Real Hybrid Shotgun addon, which shows up in the Rebirth topic. Take a look at the Rebirth thread and decide for yourself. Personally, I think the Rebirth models improve the experience, but that's subjective. However, it's highly debated as to whether the new Rebirth models are better than the originals. Rebirth is a model-replacement mod for the enemies that drastically ramps up their poly-count.

Now the one thing we need to talk about is Rebirth. SCP (gameplay bugfixes and improvements, requires to start a new game) Olfred's fixed objects (bugfixed object models) Quest Note Notifier (displays a notification for quest notes) Vurt's Organics (organic objects) - All except Biomatter and GrubPodSlimey. Vintage Song Remake (original music, better quality) Vurt's Flora Overhaul (updated plant life) Here's a copy-paste of the list from there, though you really should read Koyla's excellent guide. If you choose to add mods, I'd recommend everything from this guide (with one possible exception). Instead they're enhancements that hew closely to the designer's intent. The most popular System Shock 2 mods aren't huge game-changers that radically alter the plot. Mod the everloving hell out of it - This is my recommendation. Play it pure for your first playthrough - The game was amazing the day it was released, so there isn't really a reason to add anything to it.

Walkthrough system shock 2