There is no difference.
You sum all arguments one by one you want to sum, like{sum(Q1.NAOK, Q2.valueNAOK, count(that.Q3.sq_X.NAOK), if(Q4>3,5,10), if(Q5_SQ001=="Y",1,0),12345, Q6_SQ001.NAOK)}

Of course you can first sum parts of the questions and then the sum of the sums.
But only useful if you want to use the individual sums later somewhere.
Like (short){sum(sum(x, y, z), sum(a, b, c))}

Read the manual about it, study the sample surveys, create small test surveys where you try.