This is a problem unless you have a huge reef aquarium with plenty of open areas. Now, regarding your first question. The easiest way to separate these two species is to examine the third blue line from the head, which is positioned near the middle of the dorsal fin. In the queen angel this line is curved toward the tail, whereas in the blue angel it is straight. In juvenile hybrids this line may be curved to varying degrees, making identification dubious.
Juvenile queens also tend to be more brightly colored than blues.
For example, copperbands usually do not bother corals, but I had a customer whose copperband loved to eat her brain corals. Therefore, it is a good idea to watch this fish very closely when you place it in your reef aquarium to make sure it dose not bother your corals or anemones. If it begins picking on these invertebrates you will have no choice but to remove it. It is safe to surmise that anemones are not on the copperband's bill of fare in the wild either. In the aquarium, copperbands will regularly eat small fan and Christmas tree worms and small glass anemones, which are all similar in size and appearance.