For what it's worth, my experiences with the Nuwa update:
I did the normal upgrade through recovery. It seemed to go OK, but when I did a second reboot, the scale on my custom widgets (KWGT) became about 25% larger. And as I was also having 'problems' with the power button, I thought that I would revert to the 103. All widgets then became grey blocks.
So, I thought that I would go back to the 106. I could not get back through the recovery security to unlock the phone with my unlock gesture to re-install the 106. Fortunately I had done my back-up before I did the upgrade. As the hold-down power options didn't appear, I thought that things were really messed up.
I then extracted the 106 zip file on my computer and did a fastboot upgrade install. It's such a long time since I had done that that I had almost forgotten how to do it! Anyway, the upgrade went OK. I got back into the phone. I have now reduced the scale of my Kustom widgets by about 25%, and now all seems to be working fine, and I have changed the 'Power off or reboot' setting to what it was previously.