Voltage drops

On my first Wee, an '05 model, I ran Oxford heated grips and both my wife and I wore heated jackets. ( I think they were the 90W versions). I never had a problem with low voltage. Now, disclaimer: I disconnected one of the two head lights when using the heated gear. Also, I always had a battery that was in good condition. Now, we never had to run the heated clothing or grips at full power, normally it was likely at around 50% at most. I dressed properly for conditions and didn't expect the heated gear to do 100% of the work of keeping us warm.
On my 2017 Wee with the volt meter I never saw excessively low voltage with all the gear running. Now, I believe the '17 model did have a slightly higher output charging system so that would have also helped
Remember that heated clothing cycles off and on to maintain temperature. This is where a good battery ;pays off as it picks up the load when the gear comes on and then it catches up on its charging when the gear cycles off. This is one of the key reasons to keep a good battery in the machine as it makes a big difference. A marginal battery may start the bike but may not perform this voltage stabilization function as well. The key to any electrical problem is to FIRST insure there is a good quality, properly charged battery the system. .