DC Rainmaker is always the best guide to get to know your personal GPS enabled devices. I would recommend you search on his site for your specific models as he is very thorough with his overviews. Otherwise, please use your corresponding user’s manual. It is different for each model.
https://www.dcrainmaker.com/product-reviews/garmin
For nutrition, remember that for an Oly race, you don’t need a lot of nutrition. You do need to keep on top of your hydration and usually if you are sipping on a sport drink throughout the bike portion and then take a gel (washed down with water) and sipping on sports drink at the aid stations for the 10k, this is likely enough. If you will be out of the course for a longer period of time, then you will likely want to supplement with some extra calories on the bike to give you longer lasting energy.
However, for training, you want to make sure that you are getting in the targets that we discussed. That said, Rebecca, sports nutritionist from the Nutrition Clinic, typically does not recommend Nuun for this reason. There is little to no caloric value and little electrolyte. They have upped their electrolyte numbers more recently but it’s still not your best option. When you look at other options like Skratch, Tailwind, Osmo, etc, they have almost 3x the amount of calories for a bottle. Thus you would be better considering a sports drink that offers you more bang for your buck. Skratch is made from natural sugars so many triathletes prefer this option. This is true for Tailwind too (from what my ultra runners share with me): https://www.tailwindnutrition.com/why-tailwind/
It’s a balance to find the right amount of nutrition needed. However, the most important piece is ‘training’ your stomach to accept it. If not, you will likely end up with GI issues. So start training! 🙂
