Most of us heard of "powder douce" and "powder fort" and probably "powder blanche" as well as some other descriptives. Many of us, no doubt, would have attempted to find recipes for such spice mixtures or offered some of our own.
I would like to offer another approach to this and think back to their meaning and likely context they were written in. When we see "powder douce" should we be seeing this the same way we see "apple pie spice"? or should we be reading it simply as "sweet spices"? Look at many of the recipes these spice descriptives began in, they are full of descriptive speech such as telling us to thicken a sauce but not to make it too thick, or to make something strong enough or sweet enough, or not too much salt as well as to serve under or above something else on a platter... the list goes on and all we have to do is pay attention and maybe take them at their word.
What I am suggesting here is that we may be over analyzing, of course I did end up over analyzing to eventually come to this conclusion...
But... for an example, when looking at powder douce, perhaps it is best to look at it simply as "sweet powdered spices" which leaves it up to us to determine what powder we feel would taste best, be it one, a couple or many. The same can be said for our strong powdered spices and our good powdered spices, especially our good powdered spices. White spices may even be more of a matter of having a light coloured spice that could flavour but not colour up the foodstuff.
Of course someone who specialized in spices, or a master chef, would be well versed on what flavours would have been desirable for specific items, but we have many examples that not only give us good ideas of what spices generally showed up with what type of dishes, the spice descriptives and hints from the recipes often give us a good idea of what sort of flavour we are aiming for.
A fun exercise for anyone who would like to create definitive spice mixtures for their spicing needs would be to make lists of all the spices for your general time-frame/culture and smell and taste them. Seriously, become familiar with each of these spices and then make notes next to each one as well as determining if they would be considered a strong spice, a sweet spice, a white spice, a pie spice and so on... however many combinations you wish, remembering many may overlap. Another useful thing is to keep note where the individual spices tend to show up, and even the spice mixtures so you can keep in mind which types of food they tend to show up in.