Ok I'm gonna stop now hehe as I'm getting very confused because I just test the iphone6 again that uses iOS 12.3.1 and is slow again, so it looks like 12.3.1 is not consistent, one time it will load fast and other times super Slow. The interesting thing is on the same "Remote Preview Request" where the (Iphone6 iOS 12.3.1) loads slowly I connect the other devices that run on (iOS 13.3) and they load fast in seconds so that means the iOS version it matters after all I think.
And to samurai everything:
-Devices running on (iOS 12.3.1) the Loading Times are still inconsistent, it can load fast or it can load super slow as you can see on the video
-Devices running on (iOS 13.3) has been Loading consistently super fast since I Updated a few days ago the Chrome Desktop version to 80 and they still haven't failed even once
-So Chrome80 has something there Good that changed everything as C3 never ever loaded fast even once for me all these years prior I update the Chrome version but for some reason has to be + in combination with iOS 13.3 because I have been using -Devices running on (iOS 13.3) + Chrome79 and it never loaded fast even once.
Most of the devices I have run on iOS 13 so that's really good for me.
That's all, for now, I think the last test I did where I connect all the devices on the same "Remote Preview Request" showed that Devices that have iOS 13.3 loaded fast and the ones that have iOS 12.3.1 Still loaded slowly so it's not about my connection because otherways it will load all them fast or all slow I guess, I hope it helps.