I've heard it said there's a desired relationship between a rider's shoulder width and the handlebars they're comfortable using on a road bike.

Haven't yet been able to find a succinct description of what that relationship should be.

I'm at a point where I think my '23 Tarmac SL-7's as-received handlebar is too narrow @ 34cm for my 40cm wide shoulders (as measured to the outsides of my upper arms at the shoulder joint). Exploring what's out there now, need some idea of what to look for in a proper width.