Hello, I use PaperSpigot#110 [1.16.6]
I have 30 online players and 16TPS on my server.
CPU: intel i7 6700k
The problem is that the server still has about 3GB of free RAM, and the processor is loaded by 60-70%. Everything is set up very correctly, experience (after 1.15.2) at least chew your ass.
CPU Profiler: https://spark.lucko.me/#YDhM0szlFV