30g is just fine for angels. In 10s we are going to have someone on here telling you that they get to 10"!!! YIKES thats dinner plate sized!!!! They don't.
When you research it says they CAN reach 6" with select veil subspecies having reached 15" in the wild. Realistically they will get to about palm sized. So yes you could totally have one, or a pair even a trio would be ok.
I bread angels for years. Im a memeber of the cichlid organization, I do the fish auctions the whole gamit. I promise these people don't kow how to measure if they think they have 10" angels and likely are looking at 3-4" guys when they say they have 6" angels. I have two of my stocking lists below thats nearly 1,000 in livestock alone! I haev 3 other tanks up and running at the moment I promise Im really not an idiot and I know what im talking about.
Have you thought about rams? Bolivian or German? they are middle to bottowm fish and are really peaceful and colorful. Look them up, betcha like em
Barbs are good.
they are hearty and readily available.
If you are going to plant i would go with clown plecos for your bottom feeders, they will also suck the glass some.