I also have a USB-C - to - Microsoft connector adapter, but I don't have it at hand at the moment.

I simply used a USB-C -to- USB-C cable, as the Go can also be charged via the USB-C port.

BatteryInfoView shows a "Charge Rate" of 6.074 milliwatts with the PA-Y10. If I use the original charger (i.e. via the connector), it shows a "charge rate" of 8.250 milliwatts. So 25% slower, but I still find it sufficient. But I haven't directly compared the charging times - perhaps the whole thing will be optimised even further via the connector?

For the Surface I don't know. For me it charges everything via Lightning, Micro-USB, USB.