XCode gives a set of selectable on/off features for Texture Sets in the Attributes Inspector:
Memory: 1GB 2GB 3GB 4GB
Graphics: Metal 1v2 Metal 2v2 Metal 3v1 Metal 3v2 Metal 4v1
What do these mean?
In general, toggling one of these boxes (under the Device, Memory, or Graphics, etc. headings) adds a new "dimension" you can specialize an asset along. For example, if you toggle "iPad", you're essentially saying, "In addition to the assets I might be providing for iPhone, I want to provide images specifically for iPad." These images might vary from the corresponding iPhone images (e.g., they might have larger dimensions).
This specialization is mostly in service of App Thinning, a set of technologies for delivering smaller app bundles by stripping out inapplicable assets when delivering apps via the App Store. For example, iPad assets will only be delivered to iPads, and iPhone-specific assets will only be delivered to iPhones.
In the cases you're asking about, "Memory" refers to device memory (RAM), and "Graphics" refers to the minimum Metal feature set family and version supported by the device. Specifying an image for one of these slots indicates that it should be included in the app bundle as long as the device has at least the requisite memory and at least the specified Metal GPU family and version.
As for why there isn't a 1:1 mapping between the available options and the most recent set of Metal family/version pairs, I don't know. My presumption is that there were no differences in supported pixel formats between, say, 1v2 and 1v4.