If you’re not sure about sizing pre-purchase, it’s worth going and consulting with a fitter or detail-oriented bike store before splashing the cash. Retul, for instance, have a program (https://www.retul.com/retul-products/frame-finder/) which will help advise on the suitability of various bikes based on your dimensions. But once you know you’re pretty close and on a suitable frame size, it’s more a process of tweaking rather than looking at entirely different geometries.

In my case, the dimensions of my new bike were pretty similar to a previous bike that I’d been fitted on using both Retul and Specialized Body Geometry; I knew that the geometry was in the right ballpark, give or take a few millimetres. The key outcome from this fit was sorting out the cleat position, identifying a leg length discrepancy and adjusting set-back to counteract back-pain, and I think the fitter would have achieved similarly positive results on this bike or my previous one.

Hope this helps!