I use x3 Yamaha pedals ... Have used with old PSR-2700, Tyros5-76, and now Genos. (Sustain/Expression/Switch)
They are great pedals, but you can use any .. But make sure each pedal is separate wiring to it.
Polarity can be programmed.
I would hazard a guess that the cheap expression pedals maybe are not so smooth an action (electronically)
Al.