No, if you use the charging cable that comes with the Surface Book, nothing can break. The box on the cable ensures that the right amount of current comes out at the end. I don't think the size (mAh) has any influence, but the current (A) and voltage (V) together.

Hello, you probably mean this product here: 4smarts Micorosft Surface Connect (1m) (USB C to Surface cable?) This works fine. USB is standardised, and the devices to be charged sound how much power / strength may be delivered (protocols like QC2 QC3 https://de.wikipedia.org/wiki...) and draw it. No power is "pumped" into a device, but is always "drawn" from the user, provided the volt specifications match - which with USB is again decided by the devices themselves, or the 5V standard is used if one of the devices does not support QC. The powerbank is very practical - just make sure not to connect any devices that consume more than 80W at 230V, because then the powerbank will not work.

I would read the wattage on the original charging cable or the corresponding adapter. My laptop has 65 watts. The Xtorm powerbank has 80 watts, but I've been charging my laptop with it for a long time and often, and I've never had any problems. Our "old" Surface also has 65 watts and has also been connected to the Xtorm without any problems. I always charge with the original power supply units (for the notebook with an adapter from 3 to 2 poles.) No problems, and no overheating.