I'd like to ask the dev's what the numbers are on some of the diffs in their different configurations as i feel they're a bit off.

XRT "clutchpack" tightened/shimmed all the way is tighter than "locked". the locked option seems to slip like the clutch pack only 3/4 tight for example.

Also if you try to "convert" the RB4 to RWD (full rear split, open front diff) it still has a taste of torque steer in the steering feel and feels like the front is dragging in like an lsd.

Are these bugs or just some numbers out of place?

What makes you say locked diff is slipping more? If I do the tightest turning circle possible in the XRT with the locked diff, it generates more force (visible in F mode) than the LSD set to highest which means the locked one is slipping less (its probably not slipping at all).

Torque steer is channeled from uneven load between the tires and is amplified with open diffs. There is no defined value to get rid of torque steer, it's mathematically proportional to all the variables available.
You most likely run a rather high force feedback, open front diff and it still sends 5% torque to the front which is why you feel torque steer. There is no fix to be done to the game to get rid of it, it makes sense for the car to behave this way with how it's setup. The only thing would be if you could change the torque split to be 100% RWD.

One thing which COULD be a problem is that the front wheels have a higher moment of inertia in the RB4 than in for example the XRT because of the weight of the diff and driveshafts. I dont know if LFS takes this into account. (possibly also a drag in the diff)