I'm gradually coming round to the idea that 6x6 is the ideal compromise format.
I look at LP and CD cover photographs and I can often see ways to crop it to a rectangular format. I find it more difficult to visualise a square crop from a rectangular photograph. That is probably down to my eye not being trained enough for that. I'm sure that some of those LP/CD covers started as rectangular images.
I'm no purist when it comes to cropping. I cut my teeth on a scale focus 35mm. I soon learned to avoid parallax errors by getting more in the shot, just in case. Composition was done at the enlarger.
With 6x6 negs, I can crop to 5:4 either landscape or portrait. If the planets align, I might even get a decent square composition.