Optical triggering are of two kinds. The simpler ones trigger a flash when it receives the light from another flash. So there is now way to pass ETTL info from the camera to the flash. The IR system, like the one used by Canon, encodes the information into the IR signal and passes to the other flashes that have to be compatible to the system. Radio triggers are of two kinds too. The cheaper ones that only trigger multiple flashes and the expensive ones that pass the ETTL information too.
If you want to get your flash out of the lens axis, you have 3 options.
1) buy a ETTL cable. You are limited in motion and in number of flashes.
2) Cheap radio trigger, almost the same price as a quality ETTL cable. You are free to move around your subject but you have to set the flash manually, not a big deal IMHO.
3) ETTL radio trigger. You go “in style” but still you’ll have some issues with exposure, ETTL is not perfect for any situation
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera