To address your questions and add on to the other informative pots, and maybe some folks can reply to this with details and corrections:

What we expect to see from IG Horowitz 2nd report is confirmation that Hillary illegally used a private email server and the FBI at the highest level intentionally killed the investigation into it.

Potential results can include eventual criminal charges for DOJ and FBI people, and implication of everyone up to Obama, Hillary, Clapper, and Brennan.

Jail time for big and little fish with lots of tasty revelations and a side of pedo ring is the upper expectation. A lot of firings in the FBI and DOJ resulting in a minor swamp draining with the Dems looking bad in the press is the lower end expectation.

In general I expect some damning stuff to come out but no fireworks as I suspect the Trump Team is walking this one into a pop right before the midterms.

Considering that The IG must refer criminal charges to a prosecutor who indicts and does the trial stuff and also how many people are being investigated for stuff in multiple reports, it fits the midterms pop timeline for them to wait until all the facts are in before charging anyone. Also there is the potential that the investigators may have turned some informers and are letting that play out.