So, I've only shot Velvia 50 (have about 16 rolls of 220 and three boxes of 4x5 in my freezer). What are the differences between 50, 100 and 100F? The only thing I dislike about 50 is its poor reciprocity characteristics.
RVP 50 has the greens. With no other film are greens so well enumerated with tone and nuance than on this. Neither too weak nor too saturated for people who spend the time to understand how to exposure it well. In forests, a polariser can make a stunning transition from flat to spectacular, chiefly in that visible spectrals in an image tend to dull the effect on all of the Velvias. This film is designed for soft/diffuse light. Reciprocity of the 50 emulsion troubles a lot of people, but it is not a concern for photographers shooting
within its limits. It turns very green after reciprocity kicks in; ideal for alien star trails landscapes if that so takes your fancy! Shadows and highlights must be carefully balanced or one will be lost. Most commonly it is shadows that annoy people: large, deep, black, featureless swathes where they guy wielding the camera swears there were beautiful plants and a stream flowing through. The way to work through this is to spot meter everything. In-camera meters do a reasonable job with most evenly illuminated scenes but they do balse exposure in mixed light.
100 has pure whites but highlights blow a lot easier. It is often a good choice for landscapes where there are very strong reds, yellows and purples. Like 50, shadows block up very easily in marginal light.
100F is an avant garde palette featuring oddball mustards, yellows, browns and reds. It has never been a big seller for Fujifilm compared to the stalwart 50 emulsion.