Ok, if you add the fruit to primary the sugars will be fermented out and the flavours are different (think on how usually, the flavour you enjoy about a fruit is actually connected with the sweetness).
Whereas, if you put it in secondary, especially if you've stabilised from primary, you retain more of the original fruit flavour.
It may not necessarily take longer to clear, there's no real way to judge that, it just depends on whether you want it clear quickly or not......
Pectic enzyme is usually needed, but if it can be used before you add fruit, it sorts the pectin and aids flavour and colour extraction.
I generally add 1/3rd to primary and 2/3rds to secondary. I don't heat or process it other than freezing and thawing, which breaks down the cell walls so yeast can get to it quicker and it releases colour and flavour quicker.......