I’m just curious if nes controller extensions can cause input lag

Since it's doing no processing just extending an electrical signal no

Although the nerdy answer is TECHNICALLY yes, since it extends the cable, but since electricity runs at 299,792,458 meters per second (depending on the gauge of the wire, thanks Google), or roughly 670 million miles per hour... safe to say it won't be noticeable

But the practical answer to your question is no. It won't cause any additional input lag. The only thing that causes extra input lag would be something that requires processing, or changing of any way, the signal.

Ok thanks