I will give you this anecdote: I find BGA easier to solder than QF[N|P]. Most soldering errors I make are due to inappropriate amount or uneven solder application. No factor if the solder is pre-applied.
In production manufacturing solder paste is generally applied to BGA pads. The amount of solder in the balls is less than the ideal amount for making a good joint, and the solder paste also helps to hold the component in position.
That said, I have ‘successfully’ soldered small BGA components by just applying a sticky flux and then reflowing with a hot air gun. It can work fine for prototypes, but it’s not really how the packages are meant to be soldered.
