I am 5’ tall and under 100 pounds. I was worried this vest wouldn’t fit. However, it was perfect. I had to adjust it to the smallest size, but it was snuggly and comfy. Even with both bottles filled, the weight wasn’t an issue because it sits higher on the back. There was no bounce, but you can hear the water sloshing. It IS a bottle system, so there is nothing that can be done about that. I love the extra pockets at the shoulders, but I wouldn’t recommend it for a phone. Maybe because I have small shoulders, but I found it uncomfortable to have the iPhone 6S in it. Instead, I used a chest pocket. That worked out great.
I bought the expansion pack and places it between the bottles. It is great for keys or a light jacket.
The water bottles themselves are great, but I am not thrilled about the mouthpiece (is that what it’s called???). I swapped it out with ones I like better from other bottles. So, I am happy that your bottles are a standard size. I found that pulling it open with my teeth on the run was hard. Again, it was easy to swap out, so it should not be a deal breaker.
I would highly recommend this pack.