Cooling towers in a tropical city will just make the rooms more tropical.
Variable Volume Refrigerant is an electric or gas chiller where the refrigerant is allowed to flow to different rooms from a central location. Mini chillers appear to be where brine water or water/glycol solutions are cooled by a central chiller that again uses electricty or gas (even proprane gas).
So, in any case you will have a central chilling unit with eith the refrigerant going to the rooms or a heat transfer fluid. Given the choice, I'd go with the cetral chiller and the heat transfer fluid (minichiller). The piping to and from each room will be a nonhazardous material (use propylene glcol). You could even use the heat transfer fluid to a walk in cooler for food and beverges. The self contained chiller unit can be made very quite with insulation and proper ducting of air around it.