I play on EU servers with a wired connection and it runs well 99% of the time. Played for about 3 hours last night and had very few issues.
IMO, anyone who is complaining whilst running a wireless connection should have a long hard look at themselves and look to invest in these:
Honestly any cat6 cable off of Amazon will do just fine, there's not much of a quality difference as far as ethernet cables ago, they're just copper wiring. (as long as you're not getting like ultra bargain bin $.05 cables from China with half the internal wiring missing).
I particularly like low profile ethernet cables like these ones that are easier to hide/blend in if you don't want a thick wire running through the house.
Alternatively, there are Powerline adapters which let you use the power outlets in your house as a wired connection, but those are a bit more expensive and depend on how good the wiring is in your home.
I'm actually loving my 8Bitdo Pro 2 for this game. I might be in the minority though because I genuinely love the rear paddle buttons and don't like using the right stick (I use the rear paddle buttons for specific attacks like upair and upspecial with different profiles for different characters).