So there's actually 2 granblueversus .exe files, one is located in the main folder, the other is located in /Red/Binaries/Win64/. So in order for it to work, you have to disable v-sync in the actual 2 files: GBVS.exe and GBVS-Win64-Shipping.exe in the Nvidia/Amd Panel Settings.

Just found out that exclusively adding settings to either one or the other might not cut it out, because one might overwritte the other permission's, for example I have v-sync enabled in the "Global Settings", so executing GBVS.exe with global setting's permission might overwrite the settings in GBVS-Win64-Shipping.exe and probably vice-versa too.

Some people in the forums have proposed to use the new Low-Latency Mode from Nvidia/Amd to solve the Huge FPS Drops, but in reality all this option does is reduce your Input Delay Latency at the cost of overall performance in the game; this creates even more stutters(FPS Drops), so totally not recommended.

Only use this option if you KNOW that the game is running way above 60FPS; the game also needs to be heavily dependent on the GPU, so this trick will not have any effect in games that don't heavily demand work from the GPU and even when those conditions are met, it'll still continue to introduce stutters(FPS Drops) as stated before.

What this option does is use the old variable settings MAX_PRE-RENDERED-FRAMES and set it to 1, so your GPU won't overwork itself on pre-rendered frames in real-time, creating lesser frame-input delay.

If you really want to reduce input delay that bad, it's better to turn off anti-alias, shadow and lighting settings 'cus these make much of a bigger impact on input delay issues for the same problem MAX_PRE-RENDERED-FRAMES does - they're all processed in real time as you play the game.

Please notice that whatever is in this guide isn't supposed to fix any heavy input delay issues; this here only fixes the huge FPS Drops some players might be getting due to a v-sync bug introduced by XSeed's patch due to Zooey coming out in the game. This problem might persist in the future, so I'm leaving this here as a guide.