Congrats on the Purchase chromaniac! Well at the state things are now wonder if we'll have power and water for this year

The so called service engineers are freakin' nuts or what? Why did they not install fresh stuff and go when you were willing to pay for it?! Note your voltage and fluctuations throughout the day and the stabilizer you can get according to that. Triple Booster for below 120 volts.
The
Daikin and General A/C Units are large ones because it's almost Corporate level standard units so that there is no hassle later on down the line and maintenance is easier. If cleaned correctly by some technically sound guys then the unit will be an absolute blast when it comes to Daikin. Well worth the money as far as two years of usage of 1.5 ton a/c here.
Unit price is reasonable, but they make the most of it on the copper piping pricing and other materials. A/C showrooms will show a pipe cut on the slant to make the pipes look thick whereas anyway, generally, every A/C company will come with the same standard copper piping while fitting them. All a usual freakin' eyewash.
As far as cooling is concerned some have already mentioned the other factors, but Daikin does a pretty good job at freezing your nuts if needed! Thick and dark curtains on
Windows that have direct sunlight on them help and keeping the room airtight as possible,(flat door mats under doors, etc) also note too many iron cupboards, furniture, can also affect the cooling as they tend to absorb cooling like mad! And if asbestos roofing even with false roofing it tends to fcuk up the effect because the heat still seeps through!
Inverter A/C might help but I don't really see the technology making a MAJOR difference if the A/C is used sparingly, more useful if it is gonna be run for longer durations throughout the day and most probably if it is used year round! Hope it works out for the better in the long run for you. Note that if the fluctuations are bad the relay at the unit might burn out but they do provide a spare on board and only if the second one blows you're gonna be set back by a grand or two. Cheers and Keep Chilling!