Omg you got another angel lol! That's ok, you will just have to watch as they mature. It's a good thing Lacey is ok with the newbie so far though! The newbie is cute! I don't see any tail clamping in the pics except for the last one.
I like the big fake plant. It will provide a lot of territory division and hide for the fish. Looks like you got some java fern. Nice pick! And you placed it perfectly on the driftwood. Live plants are awesome, you will love them.
As for the carbon, I use ceramic media for my BB. Carbon will have some BB too, but it also exhausts and will seep the bad stuff back into the tank eventually (I think). So I would replace the old carbon with ceramic media. I use Eheim media but any ceramic media will hold the most BB because it is specifically designed to do so.
So you will have both HOBs on the 40g? Then it doesn't matter where the media is, just add more ceramic to the AC70.
I'm glad things are working out
Btw, I love the algae? on your caves. How did you get it to grow there?