This is according to a variety of user reports on the Reddit /r/GalaxyS6 community who claim that there are apps on their carrier-bought phones that have been removed. It should be noted that the list might not necessarily be comprehensive as there might still be some apps and features that were removed but not mentioned, but for now this is what has been found.
For example with AT&T, they have removed the Download Booster feature that basically uses both WiFi and LTE to help boost download speeds. Along with Verizon, they have also removed Microsoft’s OneDrive and the Smart Manager app, although in the case of Verizon they have removed more Microsoft apps such as OneNote, Skype, and Office Mobile. As for T-Mobile, they removed S-Finder and Quick Connect from the phone’s drop-down menu, and have disable capacitive lights, but otherwise the phone remains largely untouched.
As for Sprint’s version, they too have removed the Download Booster app and have disabled WiFi calling by default, meaning that you’ll have to enable it manually if you wish to use it. Just like T-Mobile, Sprint have also left the device largely untouched so that’s worth taking note of if you’re looking for an unadulterated experience.