I'm really happy, that you finally make it available to set the options globally on a Multisite installation. I have suggested this feature a few months ago.
So the feature is welcome, but there is an option, that is not global right now: "Automatically smush my images on upload". This option lists "all" image sizes to choose, which will be optimized on upload.
This is not Multisite compatible, as it shows only the main site's image sizes, which is definitely not valid for all sites, as image sizes are added by plugins and themes.
So I suggest and ask you to change this option on the network settings area to have a checkbox to "optimize all image sizes", which means, that on every subsite it will optimize all available image sizes.
If it is not checked, this option should show up on the subsites to choose the image sizes individually.
Please make this change, as this option with the current settings is not Multisite compatible.
Thank you for the continuous work and development!