Noel was great. They missed a trick by not bringing her into the comic adaptation of WNMHGB but I can see that a bit of her gumption is evident in NuCarol. It would have been nice if Chapel could have been written as less of a drip and a bit more up front like Noel. She never gets to put forward any kind of biological analysis for example.
Apparently Rand was considered for an early draft of the script but they felt that the content of the episode would have brought their feelings too far out in the open so they discounted it early. It's a shame actually, since Noel gets stuck like almost no other TOS female character. Giving Rand that level of activity would have benefitted her development.
Rand definitely had more chemistry with Sulu but she was more like his fag hag. It was more similar to the playful friendship she had with Uhura. I would hesitate to say it was sexual chemistry but both characters would have benefitted if it had been featured more often.