The lift is set by the springs and / or spacers. iirc the full kit comes with springs to give a 2" lift
The suspension travel, all other things permitting, is limited by the shocks. The Shocks with Gwyn's kit have 5.5" more travel than the standard shocks.
The back end will achieve most, if not all, of this potential. Basically because the linkage is non binding.
The front won't achieve full use of this - because the radius arms, with their twin mounts for the axle, are binding.
No one else seems to worry about the balance front to back though and you can't do much about it without spending a lot of money anyway. SImply perhaps - you can drill the radius arm bushes to loosen it up at the front a bit.
From your questions - you would benefit a lot from reading and digesting an excellent article in the tech section of this forum - that describes what does what in more detail than I have sketched out here.
As a final word perhaps - I would say that I think Gwyn's kit is an excellent bit of kit. Make sure you choose the brand of shocks to suit where you'd be doing your driving. Terrafirma and OME will give a better ride on the road.
hth