Using the oal_soft library (directsound device) results in choppy audio with certain sounds, so at the moment its unusable
What version of OpenAL-Soft are you using?
Specifying the sound device on the launcher doesn't appear to work (image attached), instead it chooses the first device on the list. I can work around this by deleting certain openal files (such as soft_oal)
What you specify in the launcher is just a preference, it doesn't mean that the game will actually end up using it. It will test the devices, starting with your launcher preference, then the default device, then all others, in order to find the one that meets the basic requirements that the game wants. Generally this means that it couldn't create enough sound sources on the device (it wants at least 48), although the logs don't really indicate that it skips using a device for failing a test.
Lightning/thunder noises don't work at all when using a debug build (other sounds seem to work fine)
But they work in a release build? It really shouldn't make a difference.
Certain sounds will cancel each other out. For instance in 'A Game of Tag', when you tag a fighter and the beams start firing, sometimes either the beam firing sounds wont start, or they do start but the thunder noises stop, but then there will be times that both sounds run fine (this is a case by case basis every time a new beam starts firing)
It will only play 32 sound simultaneously, so if a lot is going on then it will cut some sound out in order to play another one. That isn't new, the old code did the same thing, but the new code allows for multiple copies of the same sound to play at one time (i.e., not cutting off fly-by sounds, concurrent beam sounds, etc.). So that problem isn't new, you just notice it differently now.