I wasn't saying any of those since you didn't ask any of them in the OP.
The
iTunes scripts are like any other script: it's up to you if you want to use them. The iTunes sync script is largely replaced by the plugin in Indigo 5/6 so if you don't want to use it feel free not to (and you can delete the variables since those are now represented in the plugin). That script is typically started up in a startup trigger - Indigo doesn't start it automatically.
The iTunes Attachment script has the commands that you can use in AppleScripts to control iTunes. Again, you can use it if you like. It does have the ability to control which playlist is playing which is something the plugin can't do so you may want to look at it more for that reason. If it's in the Scripts/Attachments directory then Indigo will automatically make the handlers defined in it available for use in other scripts. No real reason to disable it.