• When I started anbox, there were multiple instances of the default apps (i.e. calculator, calendar, contact, and 4 instances of Files). Does anyone know how to get these default apps to not show up when running anbox?
• If I have to remove the default apps (or any apps I pull from my android), where are they installed to verify that adb uninstall has worked?

Ad 1 To get rid of multiple icons try to refresh the Drawer by pulling down and releasing.

Ad 2 You can remove default packages directly from an android image, see https://forums.ubports.com/post/31776 (skip media_codecs.xml step)
e.g. if you want to remove Contacts and Calendar delete the following dirs:

squashfs-root/system/app/Calendar
squashfs-root/system/priv-app/CalendarProvider
squashfs-root/system/priv-app/Contacts
squashfs-root/system/priv-app/ContactsProvider

• multiple instances: Have a look at https://forums.ubports.com/topic/3939/app-menu-double-entries-w-anbox/ . Restarting Unity8 usually helps, or restarting the device, but there is no way to completely get rid of those duplicates.
• You can't remove the default android apps. You could deactivate some calling the android Settings, go to Apps and deactivate those you don't need. I usually deinstall other anbox apps that don't work, or are not needed any more using the default android way via Settings->Apps within Anbox, too.
  Installed apps are - at least partly - stored in /home/phablet/anbox-data/data/app, but the whole content of path .../data/... is "invisible", and only accessible as root-user using a ssh or adb shell. You can navigate using cd PATH, and show contents using ls (-la].
• Easiest and fastest way to remove anbox is to reflash your device with the current version and channel using the UBports Installer; but don't wipe the user data!