i realise this is a strange question but,i have noticed that on some racing bike,s the handlebars point down slightly,is there a reason for this ? when i build a bike up i keep the bars level with the stem (looking from the side elevation)so as to keep a symmetry, (does a downward sloping drop bar create a less wind resistant riding position ? ) i have a 3Rensho which came to me like this and to me it just looks wrong,should i adjust it or leave it as is ? i know you learned lot will steer me in the right direction ! many thanks !

Personal taste, and it also depends somewhat on the bar.

On some bars the top and bottom are parallel.... I tend to see these in more level configuration when I see them.

Most bars if the top is flat, the bottom points down a little... and that is usually the way I see them oriented... I have heard that the "standard" is to point the bar's ends at the rear axle.

Handlebar question. I have only to imagine that you are referring to the actual forward facing part of the quill stem pointing slightly down-hill. To maintain a low h.bar position the stem is angled of course. What is different the past few years is with threadless stems, the way they're made, allows them to have a more right angled shape. The way old quill stems were forged didn't allow for any such design, they just have to be made longer to start with .The upper-most part, NEEDED to be beefier and at that angle to avoid flex.Quill style can't start of short then bend, they'd just flex and /or weaken. I have quills on a few bikes.To me, threadless seemed odd. I had to ask folkes about those, (threadless) designs a couple years ago.

I set my bars so that my wrists are straight when I am down on the drops. This implies that the endcaps will point slightly downward.

It's personal preference. Look at old photo's of Sean Yates and the position he set his bars at. I couldn't imagine riding with my hands in that position all day long. The tops are set at a steep downward slop while the bottoms slop upward towards him - most unusual.

I set my bars to be both comfortable and visually appealing to me - it has to look good to me. Personally I like the tops to sweep downwards slightly and generally follow the line created by the angle of the stem (I HATE the look of the upward sloping stems of the compact framed bikes - it just looks wrong to me).

The manufacturer of the bar is also important. On a track bike, using Cinelli bars, I like the bottom section if the bar to be parallel to the ground - It looks more purposful yet it is comfortable to race on.

I don't think the angle you set the bars at has any bearing on a more wind resistant position but I feel the height of the stem, out of the headtube does.

Here is how I have set my bars. ..Sounds like that Sean Yates way. I grip the bar right under the brake so that I have a tight, somewhat restricted feeling. I wrapped tape above the brake on the downward slope to such a degree that I have a little "bulge" for my palms to rest against so that I don't have to flex my wrist to the degree that I would have to if all weight had to be placed on the brakes themselves. Not elegant but I like it.
It feels the most athletic to me.

Yes - Your bars are set-up in a similar to Sean Yates. He was a 'top' rider over many years. Perhaps I should give your bar set-up a go.

I ride with them turned all the way up and use lazy levers

Me too.

Several old books, FWIW, have said to set the bars so the bottom grip below the bends angles up by 5 degrees, and to place teh brake levers so the tips are in line with the bottom of these grips. I find this looks good and is comfy in the drops if I have the right extension.

Others have said "level" and others have said point them anywhere between level and where they point directly at the dropouts. But why should pointing at the dropouts have anything to do with wrist comfort, for a person who rides several bikes of differing lengths? It should really be about your wrists, and ready reach to the controls, i.e brake levers.

Can be an issue for different bars. Cinelli 64s have the ramps pretty far sloped down in this setup, 66s (classic Maes bend, I think) a bit more level, and touring bars like Nitto Randonneurs still very level.

If you ride on the hoods a lot, rotating the bars does indeed affect the height of your hands, and thus affects your back angle.

IAB and John E have it right IMO: use your sense of comfort and ergonomics, and rotate teh bars so the bike is comfortable and most easy to ride.

Road Fan