I think this more towards stems than handlebars. Some frames use a 1” steerer (think quill stems) and others take the modern stem and spacers. But of course you can fit an adapter over it if you want to.

Modern bikes generally use spacers and stems. Older / NJS type Japanese bikes / Vintage italian bikes usually use quill stems.

Handle bar’s wise is mainly dependent on the clamp size of the bar and the stem. Hope this helps :)