If you want something to sync your tracks, look up Pluraleyes.
I use it all the time. It will accurately sync up any number of video clips. I sometimes run 4 cameras at the same time and it syncs them all up. It’s a plug in and worth the money.
Well, if I’m understanding it correctly…
what you want to do is adjust the time an FX lasts on the event. (event meaning one clip of a video on the timeline)
At the bottom of the Video Event FX you’ll see a button that says “animate”. Click it and a window will open.
Scrub down your timeline where you want the effect to change and then slide the effects at the top to make the change.
A diamond will appear where the change will take place.
You can slide these diamonds around where every you want them once you’ve placed them.
You can also click the “+” sign button on the animation window to insert another point for adjustments.