It’s my understanding that all the processing is done at the amp and not prior.If the input to the bose amp is flat, low level, variable signal (some trim levels are... some aren't), then yes. You'd use that and nix the Fix82.
If you use the outputs of the bose amp, the fix is a horrible solution. Bose uses phase EQ which will result in huge dips in the response once summed together in the fix. Bose designed this car to sound decent from both front seats via that processing method. If one wanted to create a good sounding two seat car, you'd go 1:1 from the bose outputs straight into a dsp and use NO signal delay. Just EQ and level adjustment. It wont sound as precise as an IASCA car, but itll be damn good done correctly.
Summing bose outputs is never a good idea because of this. It might sound "good" compared to stock, because phase EQ only effects certain frequency ranges (usually 250ish, 400ish, 1k), so it doesn't mess up the entire frequency range, but it'll never reach its full potential.