Can iOS apps be removed from iTunes Music Folder after upgrading to iTunes 12.7? Now that iTunes no longer syncs apps to iOS devices, can apps be removed from the folder that iTunes stored them in? (~/Music/iTunes/iTunes Music/Mobile Applications in my case)

I have updated iTunes, and was surprised to see that the applications were not deleted.
The short answer is: YES you can delete the folder.

The longer answer is: It depends on which apps you have. If you have some apps that you no longer can download from the App Store, you still need them as a backup, so that you can drop them onto your device when/if needed. So you can delete the apps that you know you still can update/download from the App Store.

And when you decide if you still need the old app, you should also see at the app’s spec. - is it a 32-bit or a 64-bit app ?? only 64-bit will work with iOS 11