Welcome to the forum
The TX40 limb had (if I remember correctly) a similar profile to the previous ML2 limb, but had different laminates to make it more stable. The TXG limb was essentially the same limb with some changes to make it a little quicker. Border has recently started using a different laminate in all their limbs, CXC, which is lighter and even more torsionally rigid.
I'm sure Sid will be along soon enough to answer more technical questions if you have any