I’m in a 13.5x19.5 rectangular room. I prefer my speakers on the short wall 9ft apart and listening about 10 ft back. Speakers are 6ft from the wall behind them. Listening chair is about 4 ft from the wall behind it. Speakers toed in slightly. I much prefer the sense of depth and a ’hall’ type resonance I get from that set up. Positioned in an equilateral triangle on the long wall gives me a more sterile sound and reduced bass energy.
If I had to deal with your room I would start with the speakers on the short wall 3 to 4 ft out into the room and about 6 ft apart with my listening chair about 3 ft into the room and go from there. Obviously actual set up is highly dependent on your room configuration including windows and doors and the sound will depend on your rooms natural acoustics as well as the effect on furniture, etc.
FWIW most folks I know who have their system in normal sized homes prefer the short wall.