I've been trying to search for some answers regarding the categories that you can choose in ambient_generic: game sounds and raw. What's the difference?

Also, some sounds act very differently. For instance a humming fan from game sounds doesn't really care about the sound boundries. I've put even 128 units for maximum audio but I can still hear the sound 1024 units away. And the play everywhere isn't ticked.

Another ambient sound, a toxic goo sound from the raw category is almost the opposite. You have to be very close to the sound to be able to hear it, even though the maximum distance is set to a very large number.

How come? Any help and thoughts are appreciated! Thanks in advance!

Game sounds are defined in soundscript files. There they have their own (overwritten) sound distance, pitch, volume and other settings. They also can have multiple sounds which are chosen randomly.

See https://developer.valvesoftware.com/wiki/Soundscripts