Hi again, that tank size is fine for angels. I think my tank is about 55cm high and my angels are adults now and they've plenty of room depth wise.
As to tetra's - I have two types of emperor tetra's. I have
Inpaichthys Kerri's - just three males remaining from my original shoal of 10
The Kerri is peaceful and easy going and will shoal well in large enough numbers. It has no special requirements that I am aware of
I also have Nematobrycon Palmeri
Now these are a total different ball game. They are territorial and so won't shoal - this is the downside. The upside is they are more stunning visually than the Kerri. With their bright blue eye and trident tail (males only) along with the bright purple body they are very pretty fish. I have 5 males and 4 females now (I lost a female last week) and I've not seen any real aggression. The males do spar but nothing major comes of it. I'd only consider these type if you plan to plant the tank as they need to have somewhere to hide and cool off when the sparring starts.
Both os these are fine with angels. Neither are nippy to my angels (not that I have seen anyway). They are also large enough not to be seen as food. Both are commonly labelled as 'Emperor Tetra' but it's obvious which is which by looking at the eye and tail. The female Palmeri has green eyes and doesn't have the trident tail.
Another I'd recommend as 'okay' with angels (if you get the angels young enough) is the harelquin rasbora. I have some Gold Headed Purple Harlequins in with my angels and the angels leave them be. They shoal well too. If you are interested I did a thread about them a few weeks ago
http/www.fishforums.net/index.php?/topic/438351-gold-headed-purple-harlequins/
Hopefully there's some useful info there for you
oh, forgot to say ... bottom dwellers? It's got to be corydoras
That's if you have a sand substrate though. Cories can't really be kept on gravel as it damages their delicate mouths