1. The fireflies are beautiful and gather on one tree, looking very much like stars.
2. The waiting time is quite long, so it's recommended to go early. You probably don't need to go to Southern Park (we went, but still did it for the itinerary; later we realized we could have skipped Southern Park and gone to see the fireflies earlier, which would have saved us from waiting so long—about an hour. The people in front have to finish before it's your turn. However, there are banana boats and small boats; the banana boat seems to be for individuals to paddle themselves. I'm not sure if you can choose that option).
3. The reason for the low cost-performance ratio is that it cost over 3,000 NTD for three people. It feels like chartering a car ourselves wouldn't be this expensive (because KLOOK also provides a chartered car, one car for three people). And it seems there are similar, cheaper local tours. However, because we were in a foreign place and worried about being scammed, using KLOOK felt safer, and the experience should be better. But if I had to choose again next time, I would probably try booking a local tour, as the location should be the same! And it would save a lot of money!