There are two types of scripts:
For full scripts it's simple: pick one. Don't use two together and don't use any extra addons. Full scripts also prohibit you from adding your own code to do stuff, pls they usually come with a whole bunch of options that you don't need or want (like all the popular scripts and their horrible colors and spam messages).
Add-ons are designed to perform only one task, which means you *should* be able to combine add-ons that were designed for different tasks, and you also *should* be able to add your own code should you want to. *should*, because there's no guarantees.
Personally, I would always recommend getting add-ons, and then pick only the ones that do something you want done. Full scripts are always filled up with a heap of options you don't need.