These files are the spinal column of No Man's Sky.
They indeed include each and every settings of the game that is not related to 3D meshes nor game item database.
There's a lot of values in them to set almost everything from wind speed to asteroid loot probability.
This is the list of the .MBIN files present directly at the root of your unpacked files :
GCAISPACESHIPGLOBALS.GLOBAL - Settings for NPC ships, either pirates, traders for combat or landing operations
GCATLASGLOBALS.GLOBAL - Some Network Settings (is this still in use ?)
GCAUDIOGLOBALS.GLOBAL - Audio settings, including Bytebeat ones
GCBUILDINGGLOBALS.GLOBAL - Base building global settings