NN sets depends on how high your wing spikes can jump like if you have nishikawa he will set high and if you have a normal A+ character he will set lower
The spike should add like a better version of yongsub bc my opinion he needs a buff bc he is the only Wing spiker that only hits 141.00km/h without any buffs
no, if anything beginner mode gives stronger spike (bc you are pulled towards it giving you a perfect set) but turning it off gives you more control of your spike
The determination passive increase stats further proportion due to skill efficiency , that means if jeahyun gain more atk,def,spd or jump his passive skill efficiency will also increase so it is basically limitless but nishikawa's skill will increase your power in a specific number when double swing or spike at 4m or higher so it isn't limitless like jeahyun passive skill