I've not been at that time, and didn't be even know they had fireworks; but if they do I assume they would be mainly on the Marina. This hotel has very obstructed views of it until the highest floors and certain rooms only.

pan pacific, MO, Marina bay sands, fullerton and fullerton bay would have better odds I would have thought

I actually did this with my wife. She is photographer so did a lot of research. You can see the Marina from Conrad but only select rooms and not best view. You would need them to guarantee room with view

in the end we went with MO. Best view and was best price for that, Marina Bay and ritz. Again be sure to book marina bay view room and email them to advise.

also do check the dates for the fireworks. For Chinese New Year they have several dates and times. Not sure if you mean Chinese New Year or 31st Dec.

To watch fireworks head over the bridge to marina and watch there we got space okay. We did one night from room and one night on waterfront for the Chinese New Year

It’s a good location for fireworks, but if you plan to stay in the room, you wouldn’t have unblocked views, more like partial views (assuming you get a room that faces the marina). The pan pacific, mandarin oriental, swisshotel or Fullerton (depending on room position) would give better unblocked views. I’ve had marina facing rooms on both NYE and CNY over the years, and although I could partially see the fireworks, it wasn’t a fantastic view.

higher level 02 series should have a good view (same as 31st floor lounge essentially) but none are totally unblocked for NYE fireworks.