Minecraft 2nd stage optimization (after installing optimization mods)

I've been hosting a minecraft server for about 2 months now, and as every fabric server owner I like optimization, and a lot of it.
For servers I have tried the Shenandoah, C4, ZGC, Shenandoah IU, Shenandoah Generational and the G1 garbage collectors mainly serverside, but I did some clientside testing too.
All of them except G1GC sucked, and I've determined that by normal usage and a test of mine.

Testing

The test I've tried:

1. Spawn about 20 players with carpet's /player command,