It all depends on how large the cage is. Budgies make very good talkers but have a bit of a squeeky voice. Cockatiels are very good at mimicing all sorts of noises. As has been said, a single bird will talk better.
However large the cage is, all pet birds are prone to obesity and expire early due to a lack of proper exercise. If you're gonna keep birds in a cage you should make a routine where the birds are regularly afforded the freedom of the lounge or wherever for some playtime. It will very soon return to its cage when it has had enough.
A Mynah bird makes an excellent talker but they need a lot more attention with their diet to keep them healthy.
It has always puzzled me why people want their bird to talk. It is not as if you can have a conversation with them. To your credit, you are looking at getting a pair. It is a delight to see a couple of birds interacting with each other.
You need not feel guilty for keeping a bird(s). All birds available in reputable outlets come from many generations of captive breeding and are as good as domesticated, just like cats and dogs.