so even if you create a PC with the generic background you still don't really miss the content if you use the pre-generated characters in dialogs?
I'm not convinced this is actually a deliberate choice. It seems a bit awkward for players to be able to simply switch characters every time a dialogue doesn't go so well. My expectation is that they've left this "multiplayer" mechanic in because they haven't built the single player equivalent.
At this stage, once companions join your party, they are essentially just additional player characters. This severely limits the kinds of inter-party interactions you can have.
I understand that there is a desire from many fans for the companions to be more Bioware-like, and this would be the ideal opportunity for Larian to implement their "love and hate" system. (How many other people will there be to develop relationships with?)
It would be awkward to have a Bioware-style companion where you can choose what they will say at any given moment. I expect they will lock down your control of companions once the love and hate system is rolled out.