Setting the water to high 1x will have no effect on your frames, and will give you a much better visual quality... even if you won't get the reflections and nice waves.
For the autogen, you can increase it but do not increase too much the "scenery complexity" slider, because it has a much greater impact on the frames (especially after having installed the reduced autogen packs). I leave it down to "sparse".
For the traffic, I could increase mine to 10 to 20% wihtout too much impact on the frames too.
I limited my ground texture resolution to 1m, mesh complexity to 19m, 100%.
My config was quite happy with that

Of course, I had to install all the files for reduced autogen textures, and I tweaked the FSX.cfg.