i like the second scenario you are going for i might do a similar one with the rainbow sharks and the 2 rams.I am in the process of setting up a 40B right now!
One of my scenarios is 6-8 Albino Aeneus Cory Cats and an Albino Bristle Nose Pleco (On black sand would look awesome!)
The second scenario for a semi-aggressive tank is a Rainbow Shark and a Bristle Nose Pleco (maybe both Albino?) Then 2 Angles, 2 Rams, and a schooling fish, maybe Rummy Nose Tetras