The no-trunks look underscores one of the stranger conceits of superhero costumes -- and one of the reasons trunks are so often part of the costumes. That's the way the legs, sleeves and trunk cling like paint, yet become suddenly undefined around the naughty bits.

Exactly. Without the trunks, it looks more like "long underwear"..or the full body tights a ballet dancer would wear. Trunks just look better. Or, if they're going to get rid of the trunks, they at least need to make the bottom half of the costume a different color. Visually that evokes the look of wearing pants...rather than a ballet costume.

The only thing I can think of for the seams being there on the chest and stomach and the mask would be if there was Kevlar underneath and the seams were their for holding it in place on those parts.

But I hate seams in general on any and all costumes... It makes the costumes appear to be "fake" like when Peter Parker would have to rent a costume when his were damaged and he had no other option.

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The reason Frank Miller retconned in was that the bright yellow is to "lure" the badguys to shoot at it, as there is armor behind it. All the bad guys in Gotham being marksmen of the highest calibre, of course!

Myself, if I was that good a shot, and Batman was coming at me, I'd aim at the lower half of his face!!

As to bright yellow costumes -- keep in mind that most superheroes wear costumes or uniforms to STAND OUT, not to blend in. Batman is something of an exception.

Do like how the cape/cowl attaches to the Bat symbol…

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The costume used in Tim Burton's films had the same feature.

"Interestingly the "Earth One" Superman doesn't include a costume make-over (except for the top of the boots). "

The costume may not be made over, but that face??  That is not the Superman I know(which of course means 90% of comicdom will love it).