It not all that different from getting a well tailored suit - every component should be reflective of your unique body characteristics.

Example: I take a size 42 in a suit off the rack but I have a shorter torso than most people my hight but longer than avg. arms. A 42 looks passable at a first glance but closer inspection shows a nice coat length but a little more cuff than desired. On the other hand a 42 tall also looks okay at first but then you'll notice that my sleeve length is fine but the coat hangs down too far below the belt. I could get away with either if I had to but the best thing for me is to get the 42 reg and have the sleeves lengthened.

If I buy a bike off the rack most lbs will tell me I should be on a 56-58 but with my short torso the TT length and ST angle on most of those sizes will put my centre of gravity too far back although the reach to the bars will be fine.

The solution for me is a 55 with a 74 degree ST and a longer stem.

Like buying a suit all of those bikes you looked at might seem okay standing in front of the mirror ( i.e. riding them around the streets near the lbs) but after a while you might notice that on one of them the ST angle is too slack for the unique length of your thighs - your knees might start to hurt and you won't get max power from your stroke. Maybe you have short arms and while the TT is right for body position you have to put on a very short stem - but if you do that the steering gets a little wonky.

Bottom line: all of those bikes probably have slightly different lengths and angles - go with the one that has the overall best match to your body and then fine tune it by making adjustments to saddle hight/ for-aft/ stem length etc. Don't make the mistake of trying to make those adjustments to compensate for poor frame geometry in the first place. Lengthening the sleeves is always better than shortening the coat.