The answer is... generally run updates first. Whether to import or export the configuration afterwards depends on who updated the contrib code base.
If you are updating the contrib code base, run the database updates and then export the configuration, as updates tend to alter the configuration storage data which needs to be commited into the version control system:
When migrating content with the Drupal 8 migrate module, the creation and updating of new entities may fire lots of custom module hooks. This may or may not be desired; if you have found yourself here, it probably interferes with the source data in a problematic way, or unnecessarily slows down the migration process.
The cleanest way I found to stop specific hooks for specific migrations, is to add a dummy/meta field to the migration and check for its value in the hook.
This is a technical description of the 3.x branch of the module. For the newer 4.x branch, see this article.
This is a technical description of the 3.x branch of the module. For the newer 4.x branch, see this article.
Apparently there are still pretty common Drupal 8 theming tasks that cannot be accomplished with the great twig_tweak module. This by the way was me giving a plug to a great little module, which makes half of all your theme preprocess hooks unnecessary.