My significant other was just there a few weeks ago, and I was green with envy -- I haven't been since '14.
I second BI's and the other suggestions below. I'd stay at the Upper House again in a heartbeat. If you can't swing that, and are looking for value, then I'd suggest the Royal Pacific in Kowloon.
I wholeheartedly second the suggestion that you visit one of the outer islands. In addition, I highly recommend a full day in Sai Kung Country Park, and in particular a visit to one of the beaches (which are much better than the beach on Cheung Chau). See link below.
Eat at Tung Po Restaurant in North Point -- if they still have the crocodile paw stew, get that. Drink at Brecht's in Causeway Bay, and Delaney's in Tsim Sha Tsui (not the one in Wan Chai). China Club is good but kind of overwrought and shiny now -- if you can swing an invite to the Hong Kong Club somehow, you can enjoy one of the dwindling outposts of real old expat Hong Kong.
For a suit, go to Sam's. I use Maxwell's much more regularly, because of pricing, but for your first one, splurge a bit. Sam's is genuinely better. Go there on your first or second day in town, because you will need to return for an intermediate fitting before they finish it off. They can get it done in a week, but you don't really want to rush them.
Skip Disney and go to Ocean Park. Funkier and much more 'local.' Seriously, it's fun, even for semi-grown-ups.
And I know that whenever I get back over there, I'll be driving the new HK-Macau bridge/tunnel. I have no use for Macau, but the bridge is apparently a wonder.
but it turned out great. Sam's is better but was closed when I went.
If you are going the Airbnb route, pay attention to the size of the apartment. Hong Kong apartments are small by western standards.
I stayed at the Upper House in Central six months ago. It is the best city hotel I have ever stayed in. The room was about 800 square feet and had incredible views of the Harbour.
Have dinner and drinks at the China Club. Your concierge can get you in. We also enjoyed Yardbird, a Japanese restaurant run by a Canadian. And rather than reading travel websites, spend some time reading the South China Morning Post online. They have some great restaurant revues.
Finally, take a ferry to one of the outlying islands. You will shocked at how beautiful some of the beaches can be.
Don't buy a cheap suit. If you want to buy a suit, do some research and get a good one.
We spent an awesome day on Cheung Chau. Some of the best seafood meals i've ever had. And then just fun hiking and exploring on a cool little island.
I suppose the first decision you should make is where to stay, Central or Kowloon. I always stay in Central--I just like it better on that side, and it's where the harbor views are possible. I don't know what your budget is. When I traveled on my employer's dime, I stayed at the Mandarin, and, as time went on, at other nice 5* hotels, e.g., Conrad, Four Seasons, and Shangri-la. But it is my first visit to the Mandarin (1975) that always sticks in my mind. When I arrived at the front door, my luggage was whisked away. By the time I had checked in and escorted to my room, my luggage had been unpacked (suits hanging in the closet, socks and undies in chest drawers), and my formal shoes had been taken away to be shined.
The suggestion to take a ferry to one of the outlying islands is a great one. If I had arrived on a trans-Pac flight, I always allocated the first day for getting over jet-lag, and a ferry trip out to one of the islands was a good tonic. Lantau and Cheung Chau are the best known ferry destinations, but there are some others that are fun and interesting (see https://www.timeout.com/hong-kong/things-to-do/hong-kongs-secret-islands).
At one end of Pacific Place Mall. Marriott was at the other end of the mall. It was right above a tube station, so getting around was not a problem. Dan Ryan's Chicago Steakhouse was in the mall (at least it was when I was there) if you want some American style food.
That location is also convenient to the tram to the top of Victoria Peak, a Catholic Church and a nice park.
Nathan Street in Kowloon has lots of shopping. I used to enjoy photographing at the Flower and Bird markets, but I am not sure if the bird market is funcional any more.
It's pretty convenient, is a nice part of town, and is reasonable. However, if you are doing a lot of business across the bay (in Central), then I suppose there are more convenient choices than Kowloon.
As for sights, the general tourist advice is probably better than I can do. I saw a few of those things (Victoria's Peak, ferries, Buddhist Temple, Symphony of Lights) and they were no better or worse than advertised. I enjoyed Kowloon Park (which was convenient to my Hotel). Avoid the Jade Market (better known as the "Market of Things that Look Somewhat Like Jade"). Eat Dim Sum and Chicken's Feet. That's all I got.