You basically need to do your research to figure out if things are patented or not. It's very time consuming and quite frankly not something that I would invest any time into.
Regarding laser cutting fabric to make a PALS grid for a load bearing purpose is claimed by several companies, but there are tons of more people who do it. I don't think their claims hold any water, but I'm no patent lawyer. Like ALWAYS, make something your own, so don't copy someones cut or pattern.
You can absolutely make flaps for a Crye vest and new vests that accept existing products. I don't know if their 4 straps are patented, but I highly doubt it because it's nothing new- or you can use a different system that works with it. Like maybe it's flawed, and can be made even better?
Honestly, you do your designs without any worry of a potential existing patent. There are patents for pretty much everything, and that just prohibits innovation if you know about them. Just don't copy anyone.
(if it's not clear, I'm obviously not a lawyer and for the most part I have no respect for broadly written patents- but I do hold design rights very high)