- modifying the region size and position when it's in use
This doesn't happen on all scenes but is based on some special materials or something else. Sometimes I can change camera tag value without see the IR refreshed. Same for the render region, on some scenes the VFB doesn't refresh...
- changing a light intensity and its position and direction ?
I think here is more difficult to avoid the refreshing, you are talking to store into the memory the light intensity and its position, but the light intensity move its radius based on inverse square area, so if you level up the light, more distance is covered so you need to render again the GI and calculation...
The position of the light is more complicated due to the same theory...you must refresh the rendering due to a different distance of the light from surfaces...
Alex