Quixel Mixer Exporting and PBR workflow through V-Ray

I have a litany of questions if anyone can answer them.

I've been trying to understand the PBR workflows, specifically manually exporting from Mixer to 3ds Max V-Ray Next. There's a tutorial I followed online and became sorta confuse at the export process: 

During the export part of this video why does he toggle of the flip Y on the Normal? Is this is always done for all external rendering programs or just Marmoset in this case? The same goes for the displacement, why did he disable normalize? And when should we toggle this option? One last question, what's the difference between srgb and linear and when should I use it?

My whole understanding of V-Ray up to this point has been specular workflows so when I attempted the roughness workflow, the results weren't accurate so I settled for specular. Additionally I had to mess around with the SRGB and Linear to get the texture map to match what I had on Mixer. With that said, what is the proper workflow for manually exporting textures from Mixer to V-ray since I haven't seen any tutorials out there available to me.

Thanks.