Tetraodontidae fishes are awersome. But i agree in the idea that are "solo" tank members. They are territorial and also could be quite predatory toward others. Also, most of them are toxic, so maybe bichir could eat food beside the puffer, but if they try to eat him... they could eventually die.
On the fact of that ornate are aggressive, i don't really know. In my limited experience(i have a pair of big ornates) i never seen an aggression between them. They tend to dominate other fishes.. but i never seen an attack. all other fish was simply scared by this "dragons" and go away letting the eat.
Funny fact, i was an "not too big fish" man too... but after i bought my first polypterus... things changed. every big tank i take was basically only for my ornates.(the bigger has 7-8 years by now)
Replying to the first issue, i think that keeping bichir as only bottom dweller is'nt a bad idea. But i've seen that plecos are not that bad as bichir tankmates. they're not so invasive an let them eat, but also devour all not eaten stuff.
Angelfish are also fine, i think, but if you have'nt a enormous tank, i suggest to keep them solo or at least not with a lot of other fishes. If the tank is at least a meter and half long, it's a good idea keeping angelfish in school(as they are gregarious fishes). It's amazing too see, expecially with banded varieties, the interaction between them.