There are some userspace scripts that will dry-run updates and email you the results. Generally it's just new config files that differ from your current versions, usually it's just whitespace differences or settings that have changed manually.

https://github.com/tavinus/opkg-upgrade is one.

As it notes, the reasons you don't want updates on auto-pilot are those config differences, and limited space available on routers.

You can upgrade packages with opkg and via the web GUI and treat it like you would any other Linux distribution when it comes to upgrades.