I'd argue that there is no such thing as identical physically. Two people seemingly built the same can differ in flexibility and strength, at least.

But to the OP's question, the key dimensions such as saddle height and fore/aft position, bar reach and height, etc. are easily experimented with. (Is that a legitimate sentence structure?) With a bit of riding one can learn whether either needs adjustment.

I have five solo bikes. They feel different from each other. Two are slightly larger, possibly "too large" for me. I can ride any of them for long distances and as fast as my conditioning will allow. (I race no one but myself.) From my perspective there is no such thing as the exact perfect fit.

Yeah, I know, I'm being a contrarian.