Purpur v1.19.2 Server Template  - "Plug & Play".

server.properties:
port = 25565 
(Default Java Port).

start.bat / start.sh Server File:
Contains Aikar's Recommended JVM Startup Flags.

If you are running with 12GB or less memory for MC, you should not adjust these parameters. 

java -Xms8G -Xmx8G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 
-XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 
-XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 
-XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 
-XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 
-XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs 
-Daikars.new.flags=true -jar purpur.jar --nogui

If you are using an Xmx value greater than 12G If you have and use more than 12GB of memory, adjust the following: 
-XX:G1NewSizePercent=40 
-XX:G1MaxNewSizePercent=50 
-XX:G1HeapRegionSize=16M 
-XX:G1ReservePercent=15 
-XX:InitiatingHeapOccupancyPercent=20

Credit & Source: 
https://docs.papermc.io/paper/aikars-flags