As far as I'm aware there are not serious problems with EFI systems provided the bike is regularly exported. However some bikes may have a lean condition and have snatchy throttles in first gear, but this isn't limited to Chinese bikes. Also Qingqi would have certainly copied or bought in Suzuki fuel mapping and EFI electronics.

I think all new bikes over 150cc in China must be EFI for emissions reasons. Having a carb bike of 250cc means you have to lie about capacity or have it off-road and unregistered only.

No idea about the differences between the supermoto and off-road versions of the bike.