Better late reply than never. This subforum is mostly dead, unfortunately. The remote can only do IR from its end, the hub can control devices via IR (either via hard wired or its built in blasters), and IP control (for select devices like Sony TVs and Rokus).

RF and Bluetooth are not the same protocol, and unfortunately, the harmony can't learn or send RF commands. The hub can connect and control some devices via bluetooth as well (windows pcs for example), but not many. The remote shows up as a bluetooth keyboard if you try to pair it with most devices.

Right now if your hub or remote has line of sight to your TV, it's probably being controlled wirelessly via IR command signals. However, if your Sony TV supports IP control, when you were setting up your Harmony to work with your TV it might have been set to control via IP (you'd know because Harmony would have asked you to connect your tv to your internet so that it could find it when you added your TV as a new device). Unfortunately, IP control for Sony TVs via the harmony is laggy, and you'll likely encounter double presses as well as the inability to turn on the tv or do long presses on the buttons.

Sine your FireTV box is a supported bluetooth device, my guess is your harmony is controlling it via bluetooth and your Sony Tv is being controlled via IR or IP.