The is the optimization configuration set for ImanitySpigot3 that does not require much tweaks, But it also may not be very well optimized for each type of servers

Some small options you may want to change to fit your case:
1. view-distance in both server.properties and spigot.yml
- View distance is a major factor for servers, most recommended value is in between 4 to 8
- But you can change it based on your server
2. entityCollisions in imanity/config.yml
- Entity Collisions used to be very performance consuming in servers
- If your server doesn't use it then disable it