So basically there is this weird bug that can happen if you use a GCN Adapter + AMD Ryzen CPU combo where the polling rate of your Adapter gets halved (~62.5Hz instead of ~125Hz) and your inputs feel less responsive.

If you use a Gamecube Controller, chances are you already use the pj64-wiiu-gcn plugin, which has a "Test adapter pollrate" function built in. (Options->Controller Plugin...) If it outputs a value similar or greater than 125Hz it means you are not affected by this bug. If it's significantly lower, you are probably affected by this. If you can't test your poll rate, try the solution anyway.

Solution: Insert the (black) plug of your adapter into a blue USB port on the back of your PC (directly into the motherboard). If you are on a Laptop, insert it into the ports labelled "SS". If it's still not fixed, try the other USB ports. Further troubleshooting:

https://www.reddit.com/r/SSBM/comments/hf41fw/solving_dropped_inputschoppy_movement_on_amd/

My game feels more responsive now, even though I didn't think there was anything wrong with it...