After looking at your equipment list, it appears that you have all FX lenses and no DX lenses, so my answer is based upon that assumption.
If you select "Auto DX crop mode" it will have no affect whatsoever when you use your FX lenses. That selection is strictly for using DX lenses on an FX camera body.
The answer to the rest of your question, if I understand it, and I am not sure that I do, is that if you crop an FX image in post processing to the size of a DX image, it will have approximately 43% of the pixels that the full FX image would have had. So, yes it makes no difference. But since you couldn't have used DX Crop Mode with an FX lens, we should change the assumption to a situation where you are using a DX lens on and FX camera. In that case if you chose not to use DX crop mode and then crop it in post, you would end up with the same pixel count as you would have obtained in DX Crop Mode.