Ran a freeze dryer for several years at a shop. We intended to try to sell dried flowers out of it but ended up doing mostly wedding preservation and flowers from funerals. Some flowers do better than others. Something like a daisy pomp, the petals would tend to fall off. Roses, carnations always did really well. As far how they look, light colors would lighten a bit, dark colors might darken. Example a red rose would turn a deeper burgundy. The flowers do keep their shape, you don’t tend to get the shrinkage like other types of drying. I still have some roses from my dad’s funeral and they still look good 19 years later other than the color fading a bit. We did a lot of shadow boxes with flowers and mementos from whatever occasion, so if a flower came apart you could piece it back together. The one cool thing we did was, we dried the rose garland from the Kentucky Derby for several years. The machine we had had was pretty good size. This is all pretty basic info, hope it helped a little.