I used "chip board" for my walls. It allows me to remove panels if I ever need to change plumbing or electrical. Suspended the ceiling so I have access there as well. I used "old work" electrical boxes so easy to reconfigure.

Water choices are copper, pex, or cpvc. You don't see that much cpvc used here in MN, but I believe it does meet code. Pex requires an investment in a crimper (or rent one). But nice for routing through walls and changing later. For the amount of copper you need, cost should not be that great an issue.

I have separate switches for white vs. safe light. The safe light switch is at normal height and the white light switch is 16" higher.

How do you plan to control water temp? Do you have just the one spout for the long sink?