I find it hard to believe with all of the control MDM provides via profiles, there isn’t a way to restrict what apps can be launched via some type of whitelist/blacklist. But dammed if I can find a way… Is there any way to either restrict certain apps or only allow a whitelist of apps?
Unfortunately, Apple does not have an API for MDM vendors to blacklist or whitelist arbitrary apps. There is only an option to app lock a device to a single app or to restrict the use of specific apps (YouTube, Safari, etc) through iOS Profiles. You can create and deploy iOS Profiles in the iOS Device Profile Configuration Dashboard.
I believe you can sort of do this by Supervising a device using Apple Configurator, then not allowing the end user to install apps themselves. This is not really the answer you are looking for, but this is not a limitation of the IEM MDM, but of the Apple APIs.