Thanks for the video KC. Interesting, and while I knew that the designer had been involved with HK, didn't realize the 516 was more or less an improved version.
Regarding the Gen 3, I don't think it is very different from the Mid-Late Gen 2 models. The gas block appears to be just lightened and simplified, and I would assume, a bit cheaper to produce, but the gas valve and piston assembly are the same as mid Gen 2, and the ambi charging handle looks like a minor upgrade that wouldn't be likely to cause problems. The other items like ambi safety and different stock and grip, seems be to details Sig seems to change periodically, perhaps just to give it some "new". I know earlier versions, before Gen 2, had ambi safeties, so it's funny how they go back and forth with certain features and hardware. It is also interesting that they have gone away from the keymod handguard and back to the older style. That was one thing I liked most about the newer versions. They've been shipping this style gas block since 2015, so I think it's past any teething.