Does using more than one event sheet make the game smoother

I know the Event sheets are read from top to bottom and there can be problems if some things are above others.

But on my game I have most animation events in one area. I have most instant variables in another area. I have most my monster's and other characters behaviours and reactions to different objects in another area and that is all on one event sheet.

Should I move things to another event sheet or will it run just as smoothly on one event sheet?

No. Event sheets are just for organisation and the number you use doesn't affect performance. In general you can check things like this yourself, although often it is a waste of time.