Based on what I've seen and read about the Switch version of NBA 2k18 it's quite solid outside of issues with story cut-scenes.
Compared to other versions, NBA 2k18 on Switch runs at half the frame rate(30fps) which makes it far less demanding on the system. The resolution is reduced, overall graphical quality is lower and cloth physics are not there, but because it is essentially the same game/engine it's very comparable; the quality of player models isn't compromised too much which is nice.
I think there's room for improvement still, but it certainly holds up well when you factor in the portability and spec of the system.
I think I'll end up going for the PC version regardless, considering I don't play in handheld on Switch that often and the frame-rate compromise, the cheaper option makes more sense for me.