Atleast on Linux, I have been able to do almost everything in 8gb without any concern but I have the macbook air which has 16 gb and this can also do everything pretty much.

So IMO in 8GB most types of coding is possible actually.

But regarding Xcode+Iphone simulator, I am not sure if that's possible tho. It's possible to run android simulator on Linux 8 GB with waydroid while being pretty smooth. So theoretically could be possible but I am not familiar with building with Xcode/Iphone simulator.