Should I use parallel lua?

I am going to make a tower defense game and I wanted to know if using parallel lua would improve the performance of my enemies.

Well, it’s always good to multi-thread if you do it properly. It depends on how you will use it, Roblox it self is very optimized either way. As long as you aren’t making code decisions you shouldn’t, you should be fine either way, but I do suggest having a look at it to see if there are any parts of your games you can use it.