A shame no one else could chime in here as I'm wondering the same.
However, I did discover that if you set the sound sources to zero-latency and mess around with the lead time miliseconds, you can get less latency. However, put it too low and you'll get voice starvation errors. A possible way around this is putting all your low latency things on their own buses. THat may help a little. Unity itsself has pretty low to no latency as far as I can tell. I'll have to do some tests.
There are a few games that apparently run in Unity that have worked though. These being (apparently) DJ Max Respect, Tapsonic Bold, INVAXION, and Musynx... although Muzynx and INVAXION do both have a bit of lag here and there. I don't know if they use Wwise. I'm pretty sure that if DJ Max Respect DOES is using Unity, it's most likely using some trade secret, because DJ Max games (all the way back to the old PC ones in early 2K all the way up the PSP, PS Vita, mobile, and now PS4) have NEVER had any lag.