In top of the other answers, Ill add some anecdotal experience in temperature management from the perspective of a desert dweller.
In this newly-ish built home (2016, but relatively new building standards for California homes) even with insulated ductwork, keeping the HVAC fan circulating without the cooling unit running will eventually circulate warm air from the attic space air warming the ducts. Effectively allowing outside hot air to heat the inside air by thermally radiating through the ductwork insulation.
And in my desk-spaces case, the room has 3 outside walls, one that is west facing therefore in direct afternoon sunlight, and a covered entryway that traps hot air and heat-soaks the walls and walkway. So, surrounded by hot air on 3 sides. Outer wall insulation should keep the thermal exchange under control, but in running network drops I found the insulation on the entryway wall lacking. On top if all that, the roof line is quite shallow over the hot exposed half of the room putting less blown in insulation between the hot roof underside and the ceiling of the room, and then there is the wooden structure directly heat-soaking with little to no length between the roof gables and ceiling rafters. All of this culminates in a room that will track outside air temps within about 5 to 8 degrees in the summer without mediation.
One thing I have done that does help when the AC is running is used a length of dryer vent tubing and a pair of old PC fans to vent the heat directly from the top of the room out of the side non-sun-facing window. Mounted one end about 8" from the ceiling in the corner with a 80mm fan in it as an intake fan(modified with a speed control knob to combat outside wind loading on the outlet fan), and the other tube end taped to an 80mm to 120mm adaptor with a 120mm fan that sits perfectly in the frame of a slide up window. Add a few old Xbox game cases and thick doubled over towel to seal off the remaining open section of window, a few shirts on hangers hanging on the blinds to prevent the frame/glass on the west wall window from driving a convection flow behind the blinds, and now the room drops down to 67F every AC cycle while only hitting about 74F between cycles on 90+F days. It can get almost uncomfortably cold if its a long cycle. Working in boxers helps too, if your home situation allows it. Keep in mind though this will be venting inside air to the outside, which will have to be replaced so overall AC efficiency will take a non-zero negative hit since its essentially introducing warmer outside air into the living space through normal air leaks somewhere in the structure.
Also, remember, hot air raises. So upstairs will always be warmer than downstairs (Id personally set up in the basement, but I'm a polar bear. The colder the better. Its easier to layer for warmth than it is to cool off). HVACs do their best to their design and implementation, but we're still slaves to the laws of physics. One possibility if youre interested with home automation is motorized dampers and distributed thermostats allowing the HVAC system to direct treated air to specific areas as opposed to circulating the entire house when just a few rooms need a burst of cool/warm air. Of course commercial motorized dampers are a bit pricey, but if you're handy you can fit steppers/servos to cheaper 'dumb' units, possibly using low cost ESP wireless serial units to a controller. But if you're not up for a week or two of fiddling, might be best to just get one or two smart damper units to just cut off larger less needed rooms and focus cooling in the more occupied living spaces.
Definitely listen to the HVAC pros in other answers. Im just some jerk on the internet sharing my experiences dealing with the effects living under our doom star. But hopefully this offers some food for thought in managing room heat. Side note: my deak space has 3 monitors (two of reasonable efficiency and one we refer to as 'the heater'), a laptop on a 6 fan cooling pad, and a PC with a 120W CPU (though its usually peaks at 60W or so under normal usage), and 3 fans (celing, stand up, and desktop) so a fair thermal load for a 12'x12' room. But keep in mind fans dont cool, they just move air. Evaporative effects of air moving over the skin cools(to a point). Every fan motor is putting heat into the room. So if you also have a number of fans the net effect will be a warmer room. However, with all of those things trying to slow roast me, the ceiling vent trick still keeps the room almost uncomfortably cold when the AC kicks on.