I was using 60 Watt heated grips for years and without any issues what so ever on my XT600 when I lived in cold climate. XT electrical and lights all stock.
The 60W setting was full power and the grips got soo hot that you had to let them go every once in a while to let the wind cool them down a bit.
If I remember correctly, the low setting was around 20W, which in winter temperatures that was not really enough.
Now in California, I got rid of my grips.