Angelphish has a great list up there for you.
Do you have a 20 long or 20 tall? What are the tank dimensions? It will make a difference in the fish you can keep in there for life.
You mean rainbowfish or rainbow cichlids?
What kind of eel are you talking about?
Completely agree that your angel will need 55+ eventually.
I personally would avoid the BN pleco because their bioload is high for a fish, so they can really limit the total number of fish you can have in a smaller tank. Just depends if the BN is something you want badly enough to have fewer total fish or not.