Is it 2-way or 1,5-way or 1-way? I mean, does the percentage adjustment of locking affects on braking or accelerating? If both, then in what proportions?

Clutch pack LSD has 2 different setings - for effect under acceleration edit power value,under deceleration - coast value. While preload was something like locking power on transition between acceleration and deceleration - or something like that,not sure...
If you're not as lazy as me,read this: http://en.lfsmanual.net/wiki/Advanced_Setup_Guide

yep, that's what i meant, but what means if u set locking at 70%(in GTIs it's not specified)? when does it lock the diff and what "power"?

Oh,forgot to check XFG/XRG - yea,they have just one setting,I'm pretty sure it's 2-way - locks in both acceleration and deceleration. LFS has couple bigger park lots - feel free to test out with extreme settings,you'll see the efect yourself then.

XRG and XFG just have LSD 1-way. LSD 1-way = LSD only active in acceleration,never in decelaration, LSD 1.5-way = LSD only active in accelaration, lsd is active in deceleration ,but not only active (is like 80/50 XRT), LSD 2-way = LSD only active in both sides (is like 80/80) some guys call this lock diff(wrong).
preload is like "minimum power" you want in your wheels . if you put much preload you can feels your car runing more than you want when you braking in LSD 1.5 way and 2 way for sure