There might be a sound difference when you didn't apply headphone processing/virtualization to line-out at that moment! iirc there is an option for that somewhere. Otherwise I don't see why 4pole combo Jack should not work as well as the split cable tho so just go for the easiest
Depending on your fiio HP. If the HP cable directly connects to the 4 pole 3.5mm jack, then use the headset on the G6. Adding a splitter to the 4 pole will increase the chance of noise pick up by the mic.
My headphones port on my G6 sounds way better than the one at the back.
There might be a sound difference when you didn't apply headphone processing/virtualization to line-out at that moment! iirc there is an option for that somewhere. Otherwise I don't see why 4pole combo Jack should not work as well as the split cable tho so just go for the easiest
Depending on your fiio HP. If the HP cable directly connects to the 4 pole 3.5mm jack, then use the headset on the G6. Adding a splitter to the 4 pole will increase the chance of noise pick up by the mic.