I have a bit of research into these guys, somewhere down the line I will get one.
They are a somewhat deeper water fish, probably most in the 60ft-120ft range, so it's greatly preferred to have a tank under 75°. Size, I wouldn't say they're any larger then a normal Dwarf angel (to spite them, depending on your view, being in a different genus, Paracentropyge), It's just that on average, larger specimens are captured. Many true dwarfs, BiColors, Keyhole (the two largest), Eibli, Half Black, Lemonpeel, outgrow the Venustus. Their diet is normal dwarf angel fare.
Unfortunately.... Because these are higher end fish, there are a number of people who would like to get their grubby hands on their piece of the pie, and that means you have a chance to receive a fish that wasn't collected healthily. The sad fact of the matter is that most Venustus either didn't receive the proper decompression steps, and/or were collected through being gassed. Some areas the fish come from are better then others, but it's still a chance. PM me you're still interested.