Where do you find bitmap fonts that are high resolution enough for modern displays?

No idea, sorry, I have never used a "modern" display. Yet terminus and the standard bitmap X fonts go to quite large sizes. They are certainly readable even when using ridiculously tiny pixels.

I prefer rendering with strict grid-fitting, with crisp stems but antialiased arcs. Unfortunately, in current Linux, it does not work even with full hinting enabled by standard fontconfig settings, one have to set magic variable FREETYPE_PROPERTIES=truetype:interpreter-version=35 .

What is the best sans serif bitmap font?

Lucida Sans.

that's not a bitmap font

Sure it is: -b&h-lucida-medium-r---14--75-75--*-iso10646-1

You could use a font specifically designed to be displayed that way.