When adding functionality to a site several aspects should be taken into consideration:
- Does the solution meet the requirements?
- How usable is the solution?
- How stable is the solution?
- Can the data be queried using Views?
- How actively maintained is the solution?
- If the solution involves contributed modules, are there any projects underway to add them to core?
I am working with the following within Drupal 8 to come up with usable stable solutions:
- Settings Tray
- Layout Builder