If you are likely to be in crowds I would want to be able to see the baby rather than having the pup on my back. Other than that I have no ideas since even as babies my dogs were too big to be carried very far.
I don't think crowds will be an issue. I think a tote would be nice so I can see the dog but since I'm short I wonder if it would hit my knees and be annoying. A backpack would be more comfortable for me but maybe not for the dog.
I bought the largest Sherpa bag they sell but found it to be really uncomfortable for me and my larger dog. It was fine for Jasper (9 pounds), but didn't work for Miracle (13 pounds). Once dogs are 10 pounds and over I think it gets hard to find a carrier that is comfortable for the dog and the person carrying them. There might be carriers that can be wheeled, but I haven't looked into any.
I bought this sling carrier to have on hand for those first two months that my mini poo puppy needs to be up off the ground while socializing in public. It is rated for dogs “up to 20 lbs” but I think that 20 lbs would be pushing it. Navy (seen munching his dinner out of toys) is 10 lbs and he fits well. It’s nice that it is a cross sling to help distribute the weight, but my back is not going to like it. It seems easy with Navy in there to switch to holding the bag in my arms if my back needs a break.
I got it on Amazon. It’s hard to tell from this picture but the dogs head is out whilst the rest of the dog is in. Much to my surprise Navy loved this thing and didn’t want to get out.
I used this style carrier for the first few months for my mini boys. I only used it to carry them up/down stairs in the house til they learned how to handle them, and for car travel til they were big enough to be harnessed in the car. A number of brands have similar styles. It's not showing in the photos but it came with an adjustable shoulder strap too.
Petco and Target carry a brand "Paws & Pals"
OxGord is another brand name, identical to P&P, found at walmart.com and Bed Bath and Beyond. If there's a choice, I had the larger size, 19"L, so we could use it a few weeks longer. The boys loved it when they were smaller.