We typically add a little kefir and a little salt to the soak water 

 I soak mine overnight and it makes cook time faster. 
It think it’s also supposed to boost nutrition. 

 It helps neutralize anti-nutrients that make seeds harder to digest.  

 I just use quick cook oats.

I wonder if the nutrition boost comes from fermentation 

 I believe so. 

 Sometime you should give oat groats a try!  The absolute best form of oats 

 I prefer the taste, it gets a tangy, sourdough-like flavor. 

We generally soak around 3 cups of oats at least overnight and up to 3 days (I'm sure you could go longer) with a 1/2 tsp(ish) of salt, 1 Tbsp(ish) of kefir, and enough water to cover. 

Soaking starts fermentation that neutralizes phytates that prevent digestion and bind to the calcium in oats so you can't assimilate it. The phytates are what give lots of people gas after they eat oats. Soaking also reduces cooking time somewhat for plain rolled oats, presumably for groats as well.