FF,
Re vaccines, I recommend following health professionals for vaccines, but that's your call.
I used the usb version, didn't want to buy batteries. I too read of failures, but took this with a grain of salt. I did however treat it carefully, obviously avoided drops etc, and packed it always amongst soft clothing in my pannier to reduce constant vibrations-- basic common sense.
Bottled water prices vary, usually more like a few dollars for 1.5 litres, but your call on if you want to contribute a few more hundred empty plastic bottles to dumps. I chose not to.
Re scooter and borders, inform yourself of duty costs of crossing borders with a vehicle, or have surprises. I personally met a couple of German motorcyclists at a border crossing who were having surprises. Gringos in cars or motorcycles can have different stuff to deal with, so look into it off you want to be prepared, your call.
And no matter, border situations can be loosey goosey , so no black and white answer.