They do have a lot of power over the device. They run the Oracle Java card standard and are a complete computer that can even run a webserver. They can interact with host events like call starting and call ending. Not sure if they can install user apps. But I have had a carrier push a voicemail shortcut into my app draw that would auto call the voicemail number when pressed. I couldn't remove it unless I removed the Sim.

A good read

Interesting that I find number 3 different for me. I have a very heterogeneous library and I find plex better at choosing when to transcode and what quality to transcode.