Every county uses ops channels slightly differently, from listening online I've found that the ops channels are usually only for major incidents (fires, major accidents, etc). Ops 7 and 8 are grouped together sometimes on incidents that require multiple ops channels, same for ops 14 and 15. Ops 9-13 are used less often and are more for special events such as SAR, hazmat, training, or PR. Responses for all calls have a main response channel, JeffCo 1, 2, or 3. JeffCo 3 is specifically used for calls that departments not on SLATER are also responding to (Washington, St. Francois, Ste. Genevieve, or certain Franklin County units).
Not sure why the audio is lower for them, but it's pretty typical for ops channels to have lower audio since it only needs to be heard by units on scene. I'm not sure if and how the tower configuration/power output is different for ops channels or response channels, but the feed on broadcastify compensates by making the dispatch/response channels deafening (Lord help anyone listening to it with headphones when tones drop...)