I concur, angelfish are not an option. But this is one of my favourite sized tanks, I got a second i liked the first so much. I too was initially considering a 20g long (intended a SE Asian biotope with small gourami) but got the 29g which is the same footprint but gives you the additional space volume wise. Tanks that are 12 inches in width (front to back) can be a bit restricting, but this one seems not to show this as much as for example my 3-foot 33g which is the same width.
I got both of mine from Petsmart. They had the tank and a hood with a 24-inch T8 fluorescent light fixture which was exactly what I wanted. Not a lot of light, especially with floating plants, but for forest fish (the sort this tank accommodates nicely) this is all the light you need. A Life-Glo 6500K 20w (24-inch) T8 tube is the only light for this tank as it has a bit more intensity than any other, and good colour rendition.
Photos below are of this sized tank. The last is the SE Asian beginning, with Chocolate Gourami and Boraras brigittae, but the Wisteria soon fell apart due to insufficient light. The swords have done OK.