![](https://lemmy.ml/pictrs/image/d3d059e3-fa3d-45af-ac93-ac894beba378.png)
Not just database migrations as others have mentioned, but database state. Databases can result in a lot of dead data, because of how transactions and locks work. Cleaning that up can cause usage of the database to be blocked for a short time. It’s easiest to do this periodically if there’s down time
Just pick a distro. It sounds like you want to learn. I suggest arch. It does the least for you, is the least opinionated, but also has by far the best documentation (arch wiki is the de facto linux documentation).
The difference between the distros is otherwise simply what package management tool they use, and what packages are in their repository. Nothing else is different that’s of any importance.