I had the same problem when I tried NEStopia so I chosed to go back to playing on my Switch console because the "tearing" became insupportable... If anyone has a solution, please help us

Due to the weird framerate that the NES runs (60.0988...) it is not perfectly 60. If you have a 60hz monitor and turn on Vsync in NEStopia, then the game will run at the same fps as your monitor (60fps). The issue is that when turning on Vsync, you will most likely feel more input lag than if It was not turned on. This is normal and it has to do with the reduction in screen tearing. I wonder what both of your monitor's refresh rate is. This will play a role in the whole situation. From personal experience when I used a 60hz monitor with no Vsync with smb1, I had no screen tearing (this will be something that can occur with different monitors) but I did have game lag/fps drops mid-run. I got a 280hz monitor, and everything is perfect. No screen tearing, minimal input lag. I'm, not the best when it comes to this stuff but the outcomes for turning on Vsync are happening to both of you (which is expected).

The graphics card that you have in your pc can also effect if you have screen tearing

I have a 60hz monitor and the Intel(R) UHD Graphics 630. Also, I was using the Nintendo Switch NES Online Controller connected via bluetooth to my PC, and the imput lag was like 3 frames. Also, I was using Nestopia 1.4

Maybe try using a different version of nestopia?

I tried using UE 1.5, but when I downloaded the .zip file and I extracted the files from it, the .exe wouldn't work, saying that some files are missing.