It looks like you've done a great job Brian
The R. papulentus is a lot like Hydrocotyle verticellata and other runner-type plants. You can clip it into individual plantlets and plant them so that they each send out runners. Trust me, you'll have more of it than you know what to do with after a while. It's still pretty rare in the U.S.
The B. japonica is a heavy root-feeder and needs to have its roots firmly planted into the substate. It looks like a grass but is actually a stem plant that puts out bunches of grass-like fronds. You'll see this when it starts to propagate. Amano uses it extensively in his aquascapes.
The Downoi is my favorite and grows in clumps, reminds me of a yucca plant. You can split the clumps into individual plantlets to propagate it, just make sure each plantlet has a decent root structure attached before dividing it. It's not very demanding as long you don't move it a lot. Under high light it will stay low, but under lower lighting it will grow vertically. In Thailand it is called "dao noi", or "little star", and you can see the resemblance. It is also a rarity in the U.S. but not for much longer.
The Ludwigia glandulosa is my favorite Ludwigia species. The color is striking next to bright green plants. It really needs a lot of light to grow well or it will lose its lower leaves. It does not branch readily either unless you let it grow to the top of the tank and bend horizontally, in which case it will put out many branchlets.
OK, I'll quit rambling. Hope you enjoy the plants Brian and keep us updated with pics of your tank. It looks great
