model file structure and naming constructions

[EagleSkinner 36]

I am slowly getting the hang of the layout of MSFS 2020 files - where models go, how third party repaints are identified and I am even understanding the confusing methods ASOBO appear to be using to apparently make life harder for third party developers and painters.

Although while I was searching and browsing I couldn't find the aircraft model files  (i.e. the Baron model is called Beech_Baron_58.mdl). Besides, in FSX the .mdl files are all huge in the order of multiple megabytes. A spot of Googling then led me to the fact that MSFS 2020 now uses .gltf files. 

For the curious layman please: What is this gltf format and why are they so small? Do the accompanying binary files have something to do with them? In the meantime, the texture files now appear to be reaching hundreds of MB for an aircraft.

How come MS can crunch the models but still need masses of disc space for the paints? Incidentally - there are some nice GA ones appearing already!