You should use a genuine charger with at least the same wattage as originally supplied. The correct wattage depends on whether or not you have the NVIdia GPU and/or whether it is 13 or 15 inches. The highest wattage chargers will work just fine (127W) as both the genuine chargers and the Surface itself have circuitry and firmware to prevent overcharging. If you originally had a 102W charger, a 65W charger may charge very slowly or not at all depending on what you are doing.
As for USB-C chargers, depends on which model Surface Book 2 - Surface book 2 USB C Charging? - Microsoft Community might be helpful. Also see USB-C high power output (85-100 watt) chargers and battery packs for Surface and premium laptops – Dan S. Charlton (wordpress.com) ****