Below is a list of tools and optimisations you can use to identify and mitigate TPS (server) lag.
It is not recommended to use anti-lag plugins such as ClearLagg - the biggest thing it does is periodically clear dropped items at a set interval - this makes a negligible difference to lag. Most anti-lag plugins have poor detection that in the worst case may cause more lag on top of what you already have, as well as hiding performance issues under a thin veil rather than actually fixing them.
Guides to Optimisation
Below is a list of detailed guides for optimising your Minecraft server through the editing of config files
- YouHaveTrouble's Guide - a well-respected optimisation resource hosted externally to setup.md
- Paper-chan's Guide - formatted as a walk-through for server optimisation
A modern performance profiler for 1.8+ servers on any platform - Forge, Spigot, Fabric, almost anything that isn't the vanilla server! This isn't an anti-lag plugin per se but it can help you find what's causing lag on your server. It now comes built-in with the Purpur performance JAR and its forks.
This plugin allows you to manage certain properties of farms on your server. Among other things, the plugin acts as a farm limiter, can remove the ability of mobs in farms to collide and perform random movements, or can completely disable the AI of mobs in farms. These actions can be performed either passively or in response to the server's performance degrading.