Would this work as a way to test optimization

[itsfsnow]

See plugin usage with no players online. Check plugin usage with 10 real players. Take second result and - from the first and divide by 10 to get average usage/player, then compare that to your server specs

Is there any better way to do this?

 

[ZP4RKER]

If I'm not mistaken, performance based on player count is not linear.

 

[Rahul.]

What is the game mode your testing?

For factions, this is what I did:
Log on 200 alts (all wondering around randomly, executing random commands)
10K spawners active
Couple lag machines
Auto-cannon firing

& had this for around 20 minutes, to look at timings to see what was lagging.