You’ve seen Jim Smith’s name on this thread and for good reason; he’s a setup guru and author of, IMHO, a must-have book: Get Better Sound. There are hundreds of setup tips, including many that address speaker placement and listening position.
I’ve listened in an equilateral triangle since getting my current speakers several years ago and felt my positioning was “perfect” for the room. But I recently revisited Jim’s book, in which he writes about “hifi” vs. “musical” sound. He makes the point that certain setups give pinpoint imaging and lots of room around instruments, which is technically impressive but for some people (himself included) doesn’t draw him into the music. He much prefers the 83% rule. Tweeter to tweeter distance is 83% of the tweeter to ear distance. I’ve avoided this in the past because I felt I might be too close to my back wall, but I tried it anyway (why not: it’s free, with no obligation!) and although I lost some hifi, the presentation smoothed out and was very easy and enjoyable to listen to. It focuses you on the music, not on the sound. So, as you alluded to, there is no “perfect” position because everyone hears differently and values different aspects of the soundscape.
Which brings me to my final comment. Just because the Jim Smiths of the world may think they’ve found the “perfect” spot for your speakers doesn’t mean it’s the perfect spot for you. He makes that point. So figure out what sound you are trying to achieve and that will largely determine the “perfect” spot for you.