New to UEFI, bootable CD and WinPE question

Got a new system that supports UEFI.  Started from scratch and put Win7x64 and Win10Pro on it. 

Discovered that the 2016 bootable CD can be booted UEFI or traditional mode.  Is it "necessary" to boot UEFI mode when working this system I've set up?  The disk is GPT - by default I guess. 

Also, I've created many custom WinPE ISO's over the years - x86 of course.  With TIH 2016, should I be able to create a WinPE that supports UEFI - which I can later mount and add my other tools to?  Assuming I'd have to use WinPE 5.x at a minimum.