I also use App Cleaner. It's a small, simple and relatively old app but it does the job.The following is one of the best and is used by many forum members. I have been happy with it.
In regards to AppCleaner, sometimes it will show all the folders and files but, it won't automatically tick every box or file for removal. If a person doesn't pay close attention, AppCleaner won't get what is listed. And as you mentioned, AppCleaner still may not get everything 100% of the time. I just wanted to mention about making sure all the boxes were ticked for any new installing AppCleaner for the first time.To do the cleanest uninstall:
1. Use the apps' uninstaller.
2. Use a removal app such as appcleaner. It sometimes doesn't get everything, but it is the best alternative if (1) is not available.
In regards to AppCleaner, sometimes it will show all the folders and files but, it won't automatically tick every box or file for removal. If a person doesn't pay close attention, AppCleaner won't get what is listed. And as you mentioned, AppCleaner still may not get everything 100% of the time. I just wanted to mention about making sure all the boxes were ticked for any new installing AppCleaner for the first time.