Questions about Xpower XTPower XT-27000 DC Powerbank 26800 mAh Li-Ion USB, DC Jack 3.5mm Black

Power supply unit, cable and a set with many different "adapter plugs"

Yes, you can use the XT-27000DC-PA power bank to connect an 18 or 19 volt laptop, but not directly via the USB-C port, as this typically supplies up to 20 volts and 5 amps (100 watts), which is not enough for many laptops. The power bank has a DC round plug (DC Jack) that can supply voltages of 5-24 volts, which is sufficient for most 18 or 19 volt laptops. However, you will need the appropriate cable and possibly a suitable adapter to connect the laptop.

You can use a universal laptop charger with 45 watts of power and a voltage between 14 - 20V Here is a suitable product: Hama Universal (45 W)

The DC output has the following output voltage levels: 12V - 16.5V - 19V - 20V - 24V.

Yes, the Xpower XTPower XT-27000 DC Powerbank can also be charged via USB. It has a USB port that can be used to connect the device to a power source in order to charge it.