I added capes to all the units in a map, and I noticed it was laging a lot. I'm guessing I need to add in something like to stop the lag, but what exactly would I put for the number? Is it the number of units with cloth on the field, or something else?

In your error log, look for where it says ClothData, raise count to at least X. Take X and multiply it by 1.15, and round up. The result is what you should raise the count to.