Your MySQL details are stored in `data/config.php`. This file doesn't exist until you installed Lychee. If you need to change your connection details, you can edit this file manually.
All settings are stored in the database. You can change the properties manually, but we recommend to use the menu in Lychee. You can find this menu on the top left corner after you signed in. Some of these settings are only changeable directly in the database.
Less means an inferiority quality of your thumbs, but faster loading. More means a better quality of your thumbs, but slower loading. The default value is 90. The allowed values are between 0 and 100.