hi there!
i have 2 boys, no helper, and live in a walk-up in central. if i am taking the boys to playgroup i often don't take a stroller and opt to carry both of them. yes you will get stronger as the kids grow. My elder son 22mths, is able to walk quite a bit now so it's been a little 'easier' these days. if we go out as a family, we definitely bring a stroller. (i've got 4 - bugaboo, phil and teds double, graco edt, and a cheap umbrella stroller which was an emergency purchase on one of our trips). Each one works for us depending on what we need for the day but lighter is definitely best. The summers in HK are really hot and humid and carrying a child for any amount of time in the heat is really tough. nice to have a break and just push the stroller.
we looked around quite a few places but decided to stay in our current flat - we've lived here for 5years now. We chose convenience over a stroller friendly neighborhood. We grocery shop, run errands, etc all as a family so it really helps to be really close to everything. We live off of Staunton St. and can walk down to Central in 10mins - no stairs. We literally don't travel more than 10-15mins ever!! Doctor, OB, pediatrician, dentist, are just on Queens Road, Groceries just up the road or organics in Central, school is a 5min taxi ride away, botanical gardens, playgroups, etc. all in the same area.
The higher up the mountain you go in midlevels, the more inconvenient it is to run around so my limit is at Caine Rd. living close to your spouses work may be something to factor in especially if he will work long hours. If he then has a 40-60min commute after work, it will be hard for your husband to see the baby before he/she goes to bed at night. Being close can also mean meeting up for lunch once a week or doing dr. appointments together during that time - which may be nice since you are new to hk.
We also use the lightest possible stroller so it's manageable up/down a small flight of stairs.
It must be overwhelming to move to HK. I moved here without a kids and found it challenging the first year or so. I just missed home so much. No matter where you choose to live, you will find a way to make it work for your family. Just pick a place that feels most like home when you walk in. In the worst case, you can always move again next year

good luck on your move!