Drupal differential db restore
This is a huge question.

I just can share my experience

First i export mysql data from live site with Backup and Migrate module.

I do restore it in my dev site. In this dev site, i beware to not send infortunetly emails, so i install Reroute email module. (great because the settings are not in database but in settings.php file)

Then i make my own dev on localhost with real datas

Depends if your have the abilities to do that, and if the datas are not so confidential to do so.

But to stick with your question, db diff is impossible is guess. And you have to upload the new module files and enabled them manually (or with drush). Settigs in drupal are totally encapsulated in db