Principles based on what? Some knowledge, or some aphorism another played has passed to you?
Playing with, and against the IQP is essential knowledge for any improving chessplayer, you cannot really get anywhere by just refusing playing such positions (which is hardly possible, anyway).
I 'm sorry that I 'm coming up with just another question again, but at this point I have more questions than answers.
Is it possible to avoid IQP and/or hanging duo pawns in QGD as Black?
If not, is the QGA a nice way to achieve that? It seems that in QGA white usually ends up with an IQP and not black, but I can't really tell if that is always the case.
As a principle, I wouldn't accept the QG. I don't like giving up a central pawn. However, I don't like the isolated pawns / extra islands of the Declined version more.