A bit of a quick advise.
It is not a secret that when testing plugins on your local PC, it is <1 ms ping environment. I.e. ideal case. You have no idea how plugin will behave when players with high ping will connect, nor how it would look like when there’s a jitter (unstable ping).
After long and painful search, I found another option: use free OpenSource software called Clumsy:
With just one button, you can set latency and many other options (“throttle” option can somewhat simulate jitter). Works like a charm. It works only in Windows, though.
P.S. Don’t forget to turn it off after testing. It is affecting your whole PC, not just Minecraft.