Doing a syncAll is a chancy thing… it literally acts like you touched each and every button, slider and control widget in your project with the last known setting, ALL at the SAME time!! Thus it is best to sync only the essential vPins, and if doing more than a few at a time (5 or so), or if some sync actions trigger longer functions calls, then running a small timer delay between them.
As for doing such after a power or disconnection event… that depends on how your sketch is set up… did the device keep running (on battery?) and only loose connection to the router is the house power was lost or is the device itself also rebooting from power outage.
I have a example of keeping your (presumably battery powered) sketch running after disconnection and reconnection. Might be something in there that helps your use case.