hey

Would be a good way to make a usamune cart, but i dont see the point for a vanilla rom since sm64 is a pretty cheap cart

1, powered splitters are recommended for svideo, i think with composite you can just use a splitter but a powered one is recommended

2, off brand svideo cables can be fine, ive heard some of them aren't great or pined out properly though but i dont know the difference

3. amarec audio definatly has a bit of lag, i listen through a line in port but you could listen through a headphone jack if you have one

Im no mod, but based on the rule

"The re-mapping scheme at the beginning of the run must remain for the entirety of the run. That is, a runner using a controller that maps buttons to analog inputs (e.g. Boxx) must use a controller with that re-mapping scheme for the duration of the run. Swapping controllers to ones with the same re-mapping scheme (e.g. swapping from OEM N64 to Hori Mini Pad) is acceptable."

Switching to keyboard would be changing mapping form analog to digital, so id say its probably not allowed.