180 x 180 pixels
App Home Screen Icon on iPhones & iPads
120 x 120 pixels
For Spotlight on iPhones & iPads
87 x 87 pixels
For Settings on iPhones & iPads
58 x 58 pixels
Also for Settings on iPhones & iPads
32 x 32 pixels
This is for macOS, not for iPhones & iPads but shows it can still be discernible on macOS if we decide to also submit for a macOS app later.
So it looks like it passes the size reduction test. The one I will submit will not have the rounded corners because Apple says those corners are Apple-generated to make sure all the apps have a uniformly-sized corner radius.