This is unfortunately an issue with the Minecraft 1.14.* releases themselves and isn't something we can do anything about. Minecraft 1.13 and newer is full of performance issues, with a much higher RAM and CPU usage than 1.12.2 and older as a result.
A number of the issues from 1.13/1.13.1 were resolved in the 1.13.2 release but it is still a lot more CPU/RAM heavy than 1.12.2 and older and is not considered 'Stable', and unfortunately 1.14 did not do a lot to improve this and in most cases is actually much worse and 1.14.1/1.14.2 have also not been shown to have improved on this much at all.
Recommendations that may help:
- Lower the view-distance in the server.properties (Files > Config Files > Server Settings on the control panel) to 5 or 6, save changes and restart the server to lower how many chunks will load in around players on the server which will help with the CPU usage spikes.
- Avoid travelling long distances quickly (ie flying around or travelling full speed by boat across oceans) as loading in a lot of chunks at once will spike the CPU and RAM usage considerably on 1.13+.
- Avoid having a lot of villagers loaded in at once as the villager AI is one of the biggest performance issues, alongside chunk loading.
- Avoid the usual potential lag causes such as mob build ups/grinders or large amounts of active redstone etc...
- Make sure to restart the server regularly (recommended at least once a day) to unload excess chunks and entities and refresh the RAM usage.
Unfortunately beyond this there is little we can suggest for 1.14.* issues currently.
With 1.13.2 it is suggested to use Spigot 1.13.2 instead of Vanilla 1.13.2 - as a number of issues in Vanilla have been patched in Spigot, so even if you never install a single plugin it will run somewhat better than Vanilla will - but currently Spigot does not have a stable release for 1.14.* that can be used instead of Vanilla.
Hopefully more 1.14.* builds are released to resolve the majority of the performance issues, as they have been reported a lot on the Minecraft bug tracker, but there isn't a lot that can be done about the issues in the latest releases.
Please note that while the Spigot 1.14.1/1.14.2 DEV builds are on our jar list currently they are not recommended for use over Vanilla 1.14.1/1.14.2 at this time. Please read the information on the post HERE in full before switching to them if you wish to do so.