Can it charge four devices at full speed at once?

No. The four connectors share the power from one USB-A port, so charging several devices at once is slower than charging each on its own cable. Expect the fastest results with one or two devices plugged in.

Which connector supports fast charging and data?

One designated connector supports Quick Charge 3.0 and data transfer at up to 480 Mbps. The other three charge at up to 3A but do not sync data.

Does it work with iPhone or Lightning devices?

No. All four connectors are USB-C, so it fits USB-C phones, tablets, earbuds and power banks. Lightning devices need a separate cable or adapter.

Do I need a Quick Charge charger for fast charging?

Yes. Quick Charge 3.0 speeds depend on a compatible QC charger and a phone that supports it. A standard USB-A port will charge, but not at QC speeds.

Is it good for travel?

It replaces several cables with one 4 ft braided cord, which suits a bag or car. The trade-off is that charging four devices at once is slow, so it works best as a backup cable.