Optical and ARC are going to be roughly the same audio quality with the same limitations. If your equipment supports eARC then those limitations are removed and there shouldn’t be any downside to connecting your source device to a TV instead of directly to your soundbar if that is the more ideal way to connect it for your particular setup.
Toslink is a technology that is almost four decades old now that wasn’t created to do anything more than stream a music CD digitally. At this point in history it now exists as something to provide backwards compatibility to older, or lower end equipment, not provide superior audio.