I'm printing a series of shots that are mostly white to off-white. What brand of fiber photographic paper will produce the most visible detail in zones above VII?
Just to be sure here...you are taking high key film photographs and you are looking for a photographic paper that will bring out detail in the upper highlight range? Something you will be exposing via either contact print or enlarger? I ask, because film can also be drum scanned and the digital file printed via ink jet...and when it comes to ink jet papers, my knowledge is much richer.
Photographic paper for film prints is a bit more complex than ink jet paper. You have to be aware of the exposure characteristics of the paper you are printing on, and find the one that will support the kind of exposure that will bring out the details you are interested in at the right end of the tonal spectrum. I don't know of many specific brands these days that will offer you much.
Ilford is the primary brand that comes to mind. Their IlfoBrom line's Galerie FB is probably one of the best fiber based photographic papers around these days for B&W photographic prints. It has a very neutral white, and should bring out good detail in the highlights or the shadows. They also have the MultiGrade line, which offers some warmer tone fiber based photographic papers. For really bright, cool tone whites, you might have to look to the resin coated rather than fiber papers. Warmer papers often lose some of the ability to retain highlight detail...they just don't reflect quite as much light as a neutral or slightly cooler white a lot of the time (although not always, there are some extremely high L* ink jet baryta papers with a slight warm tone I've tested in the past that bring out phenomenal highlight detail.)
Most brands and lines of chemically developed printing paper have different models that have different contrast ratios. Thus you can adjust the contrast ratio in the darkroom by selecting different papers.
Additionally, the "polycontrast" papers were very popular. These were one paper that could have different contrast ratios by using a filter on the enlarger. With them, one paper could do nearly pure black and white with one filter, and a full gamut of subtle gray tones with another.