I suppose you've allready got the morphology of those covered, by reading, so I won't get into that part.
Barclaya longifolia can be quite hard to get started, but once growing not really that difficult. Needs a fair amount of light ( especially the red version), and rich substrate (or root tabs)
The Aponogeton madagascariensis is not really that much harder to grow, then other members of Aponogeton. There are several different kinds of Apon. madagascariensis, with broader/narrower, longer/shorter, greener/more red-ish leaves and very high variation in how much (or less) the wein-structure is bare. Some varieties are easier to handle, then others. Nice, dark violet and scented flower-stalks are an added bonus. Though the leaves seem big, remember that there's really not that much tissue, to do photosynthesis, due to all the "holes"..... so good light is needed, as is rich substrate. They will grow better, in lower region of pH, then in serious high end.
Mick.