couple complications when building a PC for friend from old parts

Hello

So I was building(first time in life) a PC for a friend and the fans got me questioning why I agreed to this.

Spec:

  • Asus x99-S

  • i7 5820k with noctua nh-d15 and noctua fans

  • 5 uphere fans(these have molex and 3 pin connector) and 2 fractal fans(only 3 pin connectors at the end)

  • NZXT 750W

What I dont understand is how do I connect the molex fans. Do I need to connect the fans to PSU as well as 3 pin to MOBO? Can I stack these molex connectors on top of each other? Should I tell him to look for a fan controller? As for CPU cooling - Is it okay to plug the 4 pin into CPU_OPT slot? There is on marked CPU_FAN (self explanatory) and one next to it marked CPU_OPT. I've had a look at the mobo layout on asus website and from what I understand CPU_OPT means CPU_OPTional peripheral, I'm just not sure if I'm correct.

I understand these might be stupid questions but I'd rather ask here first then learn the hard way.

Thanks