If I want to add 3 more web application to my existing SharePoint 2013 farm, is that better to install SharePoint on each servers and add them via Configuration Wizard or using AutoSPInstaller tool?
it's depend, My experience with AutoSPInstaller is not good. I would recommend always install the SharePoint on server then run the config wizard manually to add the more server in the farm. may be little bit more work but save alot of unseen issues. once server add then you can start / stop the services on the server as per described role.