If you are not carrying a heavy pack, nor going over passes that are likely to have snow on them, I would say low-cut hiking shoes (rather than boots) are fine. Provided you get good ones. I too have moved from boots to shoes over the last few years, and now even have done 2 week hiking trips in the Alps carrying a pack in lightweight boots (thinking about shoes for this year but we often have to go through snow).
It's a tradeoff - shoes are lighter and more comfortable. Boots are more stable on rocky surfaces. Whichever you choose, hike in HK with them first. I would suggest Lantau 1-3 and down the Donkey Trail for anyone going hiking in Nepal - its probably one of the hardest day hikes you can do in HK, with much up and down, and will give you a good feel for your fitness.
Going to do ABC without any prior training as noted above is certainly possible, but frankly it's very stupid and you enjoy the holiday much more if it doesn't kill you.