Yesterday I reinstalled Windows 10 (Home Edition), updated the drivers, and installed the program. I have two monitors, and I use this program while gaming to dim the second monitor so it doesn't distract me with its brightness. This is a huge benefit, which is why I use Display Fusion.
And when I play (in particular in Counter Strike 2) and turn on the fading of the second monitor, an input lag appears in the game (CS2) (the effect of the enabled vertical sync)
I didn't have this problem before reinstalling Windows. What can I do? I understand it could be some hidden Windows setting I'm unaware of. Or it could be a new version of Display Fusion (I'm not sure I had the latest version before reinstalling).
Please help. This is literally the only thing I need this program for. And what I encountered is terrible and will probably make me stop using it.
I will also attach the L1 level logs.

upd: I tested another screen dimming program in exactly the same way. I have the same problem there. So, it's not Display Fusion, but Windows 10 (the official version from Microsoft's website). I don't know what to do.

22:27 enable fade
22:29 disable fade
22:31 enable fade
22:33 disable fade

When monitor fade was enabled, the game showed input lag, as if i had turned on vertical synchronization (V-Sync) - but in fact it was disabled, since screen tearing was still visible.

I apologize for blaming your program, because i tested two other programs specifically designed for screen dimming, and they produced the same effect.
Surprisingly, on the same computer, with the same configuration, the same Windows was reinstalled (but on a different SSD drive), and something happened that had never happened before.

So, I managed to remove the main part of the input lag when using DisplyFusion, the screen dimming.
First, I checked the previous disk by booting from it and running CS2, making sure that there was no problem.
Then I converted the "problem" SSD drive from GPT to MBR (just like the previous drive).
Of course, I had to tinker with restoring the boot partition, but that's another topic.
As a result, we need Legacy mode (not UEFI), and additionally, in the CS2 application properties, check the box "Disable full-screen optimization" (previously, this option did not help at all)
Unfortunately, I've become paranoid, and now I experience input lag from the keyboard, regardless of whether DisplayFusion is running.
But I really hope I'm just imagining it

I also asked ChatGPT to formulate a final answer to see why it worked. I don't know if it's correct, but here it is:

Short answer: switching the system disk from GPT to MBR forced the platform to boot and run in pure Legacy/CSM mode, which simplified the initialization path (firmware, timers, and graphics stack) and reduced synchronization overhead in the Windows desktop compositor. As a result, the end‑to‑end “input → render → display” pipeline became more consistent, so perceived input lag—especially when using screen‑dimming overlays like DisplayFusion—went down.
What actually changed
GPT implies UEFI boot with the EFI boot manager, while MBR implies Legacy/CSM boot with an MBR loader; these two boot paths initialize ACPI and timing sources (TSC/HPET/RTC) and driver stacks differently, which can subtly affect interrupt handling and DPC/ISR scheduling that underpin responsiveness.
Display-dimming utilities add an extra compositing layer; in some UEFI/WDDM setups this layer can introduce additional synchronization and buffer copies, whereas a Legacy/CSM stack on certain hardware ends up with fewer or lighter synchronization points, so frame-time jitter that feels like input lag is reduced.
With Legacy/CSM, some UEFI modules and PCIe Option ROM paths are bypassed, trimming early hooks and potential contention; on specific configurations this yields steadier frame pacing and a snappier feel when overlays are active.
Why it’s noticeable with dimming overlays
A dimmer/overlay sits between input and what’s finally presented on screen; any instability in timers, interrupts, or composition gets amplified into “rubbery” mouse or camera motion.
After the switch to MBR/Legacy, there are fewer timing and composition cross‑checks in the pipeline, so mouse and camera motion feel more immediate even though raw device speed didn’t change.
In short: the benefit didn’t come from MBR “speeding up” the drive, but from moving the whole firmware/OS pipeline to Legacy/CSM, which, on this particular hardware and software mix, removed synchronization overhead that was exacerbated by display‑dimming overlays.