Could i get some info on the difference they make

I used 5m extensions on a kite, that I thought moved to quick through powerzone, resulting in high falls and loss of power while jumping. The extensions made the kite move "slower" (it had to travel longer) through the zone, which made me feel more in control with that particular kite. However, it had probably more to do with my unexperience at the time, but it did change the characteristics from really fast flying to almost boring slow.

WHAT ABOUT FOR LIGHT WIND

If the question is: if the longer lines gave the kite more power in light winds? then no. You need a bigger kite!

It takes longer for the kite to travel from one end the wind window to the other, so allows you more easily to create your apparent wind. So yeah, it should help you have a wider wind range down the bottom end. But it will change the feeling, the kite won't react as fast etc...
But careful, some kites don't handle well the extensions, mostly because of the V, sometimes it opens the kite too much which makes it flap
(little tip if you put some on, put them at the bottom, so between your bar and your actual lines. Most of the time this is the place the lines will cross when you do a KL or just a loop. This way you will wear the extensions rather than your real lines... and that's less expensive to change!)

Cheers

Frenchie