Craizem, you've picked one devil of a topic to start off with ...
Romex, simply put, doesn't blong in anything but a wood-framed residence thats no more than three floors tall. That's what it was intended for; while the NEC has loosened the rules some, it hasn't changed the fact that the limitations of Romex quickly make it imprctical for any but the simplest uses.
A swim club would have issues, since Romex is not allowed in damp locations. (Read past the 'allowed uses' section, and you'll find this restriction).
A 'hair and nail' salon has a multitude of specific HVAC requirements. Add to that the near certainty that your original layout will not be adequate, you really want there to be some pipe - to make changes easier later.
