After setting up my A821 today, I made some interesting discoveries that I think explain what is going on with the voltage offset tests in HagssFin review and with what others found with the fan % and temp cutoff.  Several values are hard coded into the cgminer startup command and do not have some of the settings that are in the screen.  For example, the voltage offset is always set to 0 and even if you enter -2 in the miner configuration, it will not get passed to the cgminer startup.  The same holds true for the fan range (hard coded to 50-100) and the frequency.

You should be able to see this by going to the Processes screen and looking toward the bottom for the cgminer startup command.  You should be able to see what is hard coded and then entering things like voltage offset doesn't get entered here.

To get around this specifically for voltage offset, I put the following in "More Options" similar to what akadamson suggested:  --avalon8-voltage-level-offset -2

Here is a image of the Process showing te hard coded voltage offset as well as the override on more options - note I also had my offset int he CGMiner Config screen set to -2 but that did not do anything...
https://imgur.com/IhP3kSL

For those who don't know or are new to this, the command line options can be found here (just look for the avalon7 options and maybe the options for avalon8 will be similar):  https://github.com/Canaan-Creative/cgminer/blob/master/README