It doesnt depend on one specifik graphic setting! It mostly depends on the GPU utilization. When you put all graphic settings to high or max, GPU utilization goes up. Higher graphic settings = more GPU utilization = more input lag.
It doesnt matter if you have shadows on, or anti-alaising. The question is how much does anti-alaising affect the GPU utilization?
Anti-alasing has little affect on the utilization. Shadow settings like: Post processing quality, shadow quality, shadow resolution etc. have the biggest affect on the GPU utilization! Also, your display resolution has a big affect. You will get less GPU utilization with 1080p rather then 1440p.
Now, how much % Usage should your GPU have to get low input lag? At 1%-80% utilization you will get very little input lag. You will get the most input lag if your GPU is at 90%-100%.
Now, how can you reduce input lag?
Reduce your graphic settings to your liking. Personally, I like to have my settings on medium, that way I get good graphics and max 80% GPU utilization. But if you have a low end GPU, you should put all settings on lowest.
You can also cap your frames, this will reduce utilization too and you can still play with high graphics!
Its important to cap your frames to your minimal FPS.
For me, I get at least 60FPS even on high graphics and I still have low utlization. But as soon as I get 80-100FPS, my GPU is at 90-100%. So I cap my frames at 60FPS, that way my gpu is not maxed out and I get low input lag.
There are many ways to reduce your gpu utilization/input lag!
I hope I could clarify you, and also help.
(btw, check out "BattleNonSense" on youtube! He tested this methology and got the biggest input lag reduction! He even compared "nvidia reflex" vs capping your frames, and he got less input lag with capping frames!)