The Texture Emission type allows any valid texture type to set the light intensity. Texture Emission now uses texture instead of temperature value. Actually, Blackbody Emission still works, but there is no Kelvin mode. Texture Emission is an important choice, and with this feature you can make many effects, such as a projector, a cinema screen or a TV screen.
For the projector example you can see this section.
Efficiency or luminous efficacy?
Texture Emission is also used for "Light efficiency". What is this light efficiency? Let's briefly explain:
The luminous efficacy is the name given to efficiency, which indicates how good and sufficient the light of any light source is, and which is visible to the human eye. To make this definition easier, we can give an example of a lighting source that we often use at home, like bulb light.
The light level that the bulb we use at home is directly related to the power (Wattage). Think of two bulbs of the same type, 50 and 100 Watts: If we compare the lighting power between these two, a 100 Watt lamp will result in better illumination. However, if you have two lamps of different types, it would be misleading to say that the stronger between the two will illuminate the room better.
For example, the light yields of incandescent filament lamps (classic light bulbs) are lower than those of LED lamps. This means that a 25 Watt LED lamp can easily provide the similar lighting power of the 100 Watt incandescent lamp.
Let's ask the obvious question: "What does this have to do with Octane?" If you do not intend to make a realistic render, the question is obselete. But if you want to get a realistic render, especially if you want to get an indoor render, it's very important to know the realistic lighting power of the lights (actually it's always important). If an interior designer wants to design a lighting system, he does it with the "Lumens" unit, not the Wattage unit. Unfortunately there is no use of Lumens in Octane (Why? Nobody knows). However, you can assign it to the Texture section with the "Float" value. How? Since this topic is quite technical and complicated, we will be able to direct you to a few links.
First of all, you can follow the "Lumens / Wattage" topic in the forum from this link.
If you want to get detailed information about light efficiency, you can go to this link.
Light efficiency is a beautiful and interesting topic, even if it's cumbersome in Octane, it will add a lot to your renders.