Hmm I’m not certain I understand your question, so I’ll state what I know: the stats displayed are width, height, depth, channels. 32-bit float is the default data type. If you define a new image with:
gmic 800,800,1,3
that will imply 800 * 800 * 1 * 3 * 4 bytes (32bit = 4 bytes per pixel per channel). For a three channel 2D image that means each vector valued pixel occupies 3 * 4 = 12 bytes (you can have arbitrary number of channels). The data is stored in memory as complete channels, rather than all bytes of a pixel in turn. For an rgb image it’s in memory as all red pixels, then all green pixels…
Whether other data types can be selected, I think so but @David_Tschumperle can elaborate (it used to require extra compilation steps).