Soul Charge has no delay

I'd like to note that EMS got the swing/haxfully fast Soul Driver as well.

Does this super speedy enchantment apply to NLs too with Shadow Claw? I always see them buffing it in between attacks with almost no delay.

Yes shadow claw has little to no delay. However, while theirs is super fast as well, you can use soul charge while attacking. I've used it in the middle of spamming driver plenty of times.