I have found the opposite to be the case. I worked on a team of 14 on a very large, old, and well-established 5-star app, and I did not notice any significant Xcode workflow performance gains when I went from a 8GB MacBook Pro to 16GB. Similarly, when we decided to buy a 12-core, 32GB Mac Pro for our primary CI workstation, the build time improvements were underwhelming. Above the level of a competent modern MacBook Pro at 8GB, there is surprisingly little ROI at throwing cores and RAM expecting big gains , its just doesn't scale that way for reasons I've never been able to find online.

Ive been developing iOS apps since the App Store launched (app #1001), and found that my development laptop requires far less storage than my home machine. Your main storage will be your app repository, and even some of the largest ones Ive worked on with 14 devs were smaller than 10GB and don't grow fast (if they are bigger they should probably be pruned or truncated for age). I don't typically keep original or draft mocks or art on my machine, they are all on cloud servers, so the only assets on my machine are the iOS optimized ones in my repo. The one difference is 3D games. I developed a 3D game and VR experience with Unity for iOS and managed a lot of the original 3d assets, that was pretty huge.