If your house keeps out the cold, wind and damp, it will keep out the heat. There is no special way for walls, windows and insulation to let heat or hot air pass only in one direction.

Florida is unbearable even for the people who live there.

I’d set my self on fire before stepping foot in Florida

I lived in Florida and now I'm in Europe and honestly give me Florida.

The outside is bearable to me, but cooler than Florida is this time of year. The issue is there's no escape. AC is incredibly rare and even the few stores that do have it don't crank it like Florida.

I wake up its hot, I go out its hot, and I go to bed its hot.

Back in Florida it was hot while I waited for the car AC to kick on, the office was cool, and my house was cool.

Having no break from the heat is brutal

Don't know about their unit, but my one is 48KG, so lugging it isn't the easiest.

I would've though have it setup at the bottom of the house, have it running and only open a window at the top of the house...

Assuming no major air leaks in the house, the cold will displace the heat starting at the bottom, the rising heat then able to escape out of a cracked window at the top of the house,

Otherwise have it at the top of the stairs and hope that the falling cold will displace the heat

Those are very sensible suggestions tbf; it's just that my house is really small! I live alone, renting. My room upstairs doesn't fit any more than my bed and the AC (floor unit). The only way I can work up there is with a laptop on my bed, which is an ergonomic nightmare that will have me cramping in about 10 minutes.

I have a small sofa that is comfortable enough to sleep on downstairs, that I would probably use if I did not have the AC

I can lug the AC up and down the stairs but one of those 2 areas will be so warm that by the time I've moved it I'm immediately in need of another shower... and then again when I move it back.

Blackout curtains + closed windows do not keep my first floor anywhere near cool enough unfortunately; I think it's really poorly insulated as it is also really cold up there in the winter (though this is much more manageable to me.)

My problem with sleeping with a fan is they trigger my myofascial pain syndrome quite badly. My only relief is still air that's cooler. I also run quite hot in general :/

I have noticed, however, that I can do a single top up at around 13:00, where I run the AC for a bit to get the upstairs room slightly cooler than downstairs. Then I turn it off and close the window and it stays somewhat bearable for the rest of the day, opening the window again at night.

I completely understand your concerns about power usage as I am eco-conscious myself, and I really wish I had a ceiling fan to use instead. Getting my landlady to sign off on that is a bit unlikely.