bunrattyMKS,
Out of all the options that I have tried yours is the one that I noticed had the biggest impact. [for everyone's reference, it was to turn off Siri) I can't say that the battery drain has been completely reversed to how it was prior to the upgrade, but it is lasting a little longer. So I really appreciate the advice. I've seen people comment here with iPhones 7, 8 and Xs having battery drain issues because of this upgrade, and some of the even changed out their battery to no avail. So I'm going to live with it until my phone until it breaks. Because my conclusion from reading this insanely long thread is that the final solution is to move to Android. It was a good journey.