There's a lot of ways to tie down NODs. I've been to different training that all required different tiedowns for various equipment, but the simplest way is to route gutted 550 around the body of your -14, secure it to itself with a weight bearing knot, then make a separate loop with a weight bearing knot that you attach a small carabiner to. You can keep it secured within a pouch this way, then simply attach the carabiner to your helmet (either another loop of 550 on the shroud, a piece of nylon on a helmet cover, a helmet band, whatever).
https://i.imgur.com/6VWzdYV.jpg
https://i.imgur.com/zS3f1qN.jpg
It won't win cool points on Instagram, but the guys who knock tiedowns most likely never had to tell their Squad Leader that they lost their NODs. It's been 11 years and I'm still sore.
The helmet lanyards do nothing to secure your NODs in a pouch; where they will live the majority of the time.
I keep my PVS-14 secured to a carabiner within a small general purpose pouch and use a SAM splint as a protective insert.
As for helmet/etc;
1) The Norotos Dual Dovetail Adapter is fantastic.
2) Go with the G24 if you can afford it. They keep a lower profile when stowed than Norotos arms, and this is from a guy that uses an AKA2 and wishes it was a G24.
3) Team Wendy Exfil LTP; you'll love it.
4) If your NODs are stowed, just turn them off. Yes; the DDA will maintain the auto-off function. It will not turn back on- it simply kills contact when stowed and you have to manually turn it to off and then back on again. So if you're gonna stow a PVS-14...just turn it off.