The expression "¡Qué cosas tienes!" is used to expressed surprised for something positive or negative.
¡Qué cosas tiene la vida!
Life surprises you!
¡Qué cosas tiene el amor!
Love makes people act in amazing ways!
¡Qué cosas que pasan en una guerra!
Inconceivable things happen during war!
The expression "no es por nada pero..." is used to express an idea that may be contrary to the listener's point of view or objectives. For example:
No es por nada, pero creo que lo que estás haciendo está mal.
I do not mean to be rude, but I think that what you are doing is wrong.
No es por nada, pero creo que eso es innecesario.
It is not a big deal, but I think that is unnecessary.
No es por nada, pero él ya se fue-
I do not think it is important, but he already left (so there is no point in going there now).
The closest English translation to this that I can think of is "I am just saying..."
As for "qué cosa"... I am not sure, I would need the context in order to tell you more.
I hope this helps.