So companies on here like Horticultural lighting group , timber and diyled (who sells HLG lights and his own in uk) will all list the actual watts the board or strips use. Some may be cranked up slightly over the listed wattage, like a hlg135w kit will go up to 150w.
With that level of efficiency you can use less power to produce more light than HPS, with cheap lights on amazon it takes around the same power.
The confusion with lights like mars or vipar spectra or any other Chinese light is that they take the number of diodes and multiply that by the max wattage of the diode. So you have 500 diodes at 3w and they call it a 1500w light, but the diodes will never run at that because they would burn out so they massively underpower them to prolong the life of the light (which is normal for LEDs) So you get a light that's called 1500w but is actually 270w In power it uses. Its mostly a sales tactic to sell shit lights.
There really is no comparison between old blurple tech made from the cheapest parts and what we use these days, been white strips,cobs or boards paired with the best drivers on the market. The only similarity is they are all LEDs. But as far as performance they are worlds apart.
I second diyleduk since I bought my last HLG quantum board from him and he's a sound bloke and a member on here.
Also you said you havd a 3.6x3.6 tent and said 90cm x 90cm, but 90cm is 2.95ft so im not sure if you have a 90cm x 90cm tent or bigger.
If its 90 x 90 cm then 260w QB kit or similar wattage of scope strip light is fine. I would probably go for the scope for more light spread and better uniformity.
Now you also said you had complaints form neighbours over noise. Fan hum can go through a brick wall like a knife through butter. Its the frequency of noise that is very hard to stop.
If you want a truly quiet fan I will link the one I just bought. Its 25db, which is really quiet, my old Isomax airforce 2 silent fan was 50db, most fans are in the range of 50db give or take, but the decibel scale is not linear, google it.
So its almost silent in the room and cant even hear it through a shitty wood door nevermind a brick wall.
https://www.ebay.co.uk/itm/Hydroponics-Silent-6-Inch-150mm-370m3-h-GROW-ROOM-ACOUSTIC-BOX-EXTRACTOR-FAN/262879275996?hash=item3d34d36bdc:g:fMgAAOSwHSRbs0eh:rk:13:pf:0
Im only running a 2x4ft tent with a 260w QB at the moment, I should of gone with the 4" fan because even with a digital speed controller running the fan at less than half speed I only get about a 3 degree rise from ambient with lights on.
Anyhow I cant stress enough how much more comfortable I am running this fan, its the best thing ive bought in ages. I used to run rucks, airforce 2 silent, all boxed in with acoustic material to muffle the noise, it was never quiet enough for my liking.
This fan takes the piss, you have to double check its on its that quiet.
