Use this world to stress test your PC and measure your FPS and Lag Spikes. I created this world on a flatworld setting and it contains villages, villagers, animals, lava, water, and your character will be on an automated rail system. When you first enter the world you won't have to do anything as the character should already be on rails.
Instructions
1) Turn everything in Video Settings to the Maximum value. All sliders to the maximum as well.
2) Change FOV to Quake Pro
3) Use Alt+F3 to see your system data including lag spike information. Consider using a FPS counter such as FRAPS or MSI Afterburner to see your fps in game.
Measure an average in Vanilla game. Then use the same test with Sodium mod and OptiFine mod.
You can do this with multiple mods/modpacks to test your system performance.
Note: There is a lot of stuff happening on screen so this test will have a very heavy impact on lower end machines. If you are on a low end PC then consider turning off the thunder (/weather clear) and try testing on Medium settings and Normal FOV.