If you have swap file turned off or lowered to minimum then all of them. Not everyone uses PC like you do ;)
Complete nonsense. None of those games need more than 16GB of RAM (or even that much really). I don't know of any game that does. Of course, how much RAM you need will vary based on how much crap you have running in the background. Any normal user looking to play games is going to struggle to fill up even 16GB though.
Not even remotely true. Most games barely use 10gb, as long as you don't have a bunch of rubbish running in the background.
You’ll be fine on any of the latest games with 16gb RAM. 32gb only really needed for photo and video editing etc. No harm in future proofing though.
Try to put one stick and boot and then add second one.