SS100 is in steam, for people who use that. TAA is render scale in the sim itself. OXR is OXR, correct.
You should be getting at least 40 FPS with your setup and the correct settings. Try OXR70/TAA100, LODs 100-150, medium clouds, no ambient occlusion, no bloom, no light shafts and switch off anything else you don’t particularly care about (for example, I have reflections off).
In general, there are some good really detailed posts on this forum for optimizing performance, such as the current one, but also others, like this one: VR Bang-For-Buck Performance Guide