Hi ludwig.lindstaal,
Platform Default right now maps to Async and Cache.
Baked means we save the substance texture data to disk, rather than invoke the substance engine when the project runs.
On Load means we load the substance materials when the level loads. Sync means it will freeze UE4 while it does it, ASync will load them in the background.
Cache will store the substance texture data the first time the level loads, so the next time the player loads your game, it will load from disk, which can be faster.