You need QCHAIN if you attempt replace a file with a previous version. If this is not the case, you do not need it. In order to know that, you will need to study the contents of each update (which apparently you have done). As for the best order, again this should be determined from the file version number of the updated Windows files. Now, theory aside, I install according to 6 digit hotfix number. I have tested with and without QCHAIN, and the results (for that given hotfix set) were identical. Still, QCHAIN is cheap enough and easy enough, I always use it, so I do not need to worry about it.