World settings are stored in a different folder compared to the main server settings
server
|-----> config.json (for server general settings)
|-----> universe ----> worlds ----> <world name> ---> config.json (For world settings)
So to change settings like enabling PVP you need to go to the world settings config.
By default, your world is called default
How to modify world settings:
1) Go to File Manager in your Control Panel
2) Go to universe folder
3) Go to worlds folder
4) Go to default folder (or the world you want to edit)
5) Right-click the config.json file and click Edit
Examples of settings you can change
IsPvpEnabled - Allow player vs player combat (false for off, true for on)
IsFallDamageEnabled - Players take fall damage
GameMode - Default game mode for this world (Once a player has already joined, changing this setting won't take affect on them)
Available game modes:
Adventure - Standard survival gameplay
Creative - Building mode with unlimited resources