My take on handlebar position - what I want is the handlebars located so my shoulders are supported the proper distance ahead and above the seat with comfortable bend in my arms. So 1) this is dependent on where the seat is located. For me, this varies by bike and purpose. For fix gears, my seat is not far behind the BB and I have a near horizontal back with close to straight arms when in the drops. Ie, as comfortable as I can get if I have to spend the next 20 miles upwind in too big a gear. For pure road bikes, I rotate my whole position back a touch. Seat back say another 1/4". Bars a little higher and back. For gravel, seat comes back maybe another inch and bars a bunch further back and higher. All this while keeping seat to BB to handlebar triangle the same except for the rotation about the BB.
Having established 1) above, I go on to 2) the handlebar" line". I find that once I have the handlebars in the perfect place, I can pass an imaginary line through the tops, then move the handlebars anywhere on that line (within reason) and hae equally comfortable although slightly different hand positions.
That "line" is: viewing the bike from the side, a line that slopes up and forward. For me, the "slope" is 2 cm horizontally forward by 1 cm of steerer spacer or quill raise "up". (Quotation marks because this is not horizontal-vertical X-Y but oriented to the traditional bike parameters of quill stem length and steerer height along the head tube angle.)
So, once I have the bars at the proper location to orient my shoulders with comfortable arms, I can move it anywhere on that line (which is an approximation to the arc my hands would follow if I swung my arms). So I can go low and close or higher and further forward at equal comforts and power. The high/forward position gets my forearms more horizontal and is more aero. Low and close is more direct pulling power for uphill power out of the saddle (though the further forward bars are more comfortable for very long out-of-the-saddle climbs). Too low and close and I hit the tops with my thighs out of the saddle. I commuted for a while fix gear with often strong headwinds using a Zzipper fairing. The high and far forward position worked really well!)
Cool thing about this approach - I can measure up a frame I am looking at, sketch it up that night, locate my shoulders and the "line" on the drawing and quickly see what stem would be needed to make that bike work. And since raising or lowering the stem moves the bars at close to right angles to the "line", I can almost always make a frame "work" and be comfortable. The next question is do I want this frame (which is say- pure racing) with the bars that far out there? "Nah, I'll pass". Or the small Raleigh Competition - "hmm. low and close with the 13 Pearl in the box would work well. Fun!" I bought it with no regrets.
And lastly, off the same drawing I can now calculate my weight balance between the wheels. Do I like it? I've passed on frames that flunked that part.
Ben