Folia
Multithreaded Paper fork
Multithreaded, CPU Cores Help
Folia splits the world into independent regions, each ticked on its own thread. Unlike vanilla or Paper, adding CPU cores does improve performance, but only when players are spread across the map. Players crowded into one area share a single region and thread.
Plugins Must Support Folia
Most plugins do not work on Folia. Only plugins explicitly built for its regionised threading will load correctly. Check for Folia support before installing anything.
EULA and RCON
On first start the server stops and asks you to accept the Minecraft EULA. Read it, set eula=true in eula.txt from the file manager, then start the server again. RCON uses the password and port from your Startup tab. The in-panel console connects to it. You don't need to touch server.properties.
Official Documentation