What is the exact difference between a Bitcoin and Bitcoin Cash raw transaction to address sighash_forkid?
Bitcoin Cash changes the sighash preimage to the one that is used by segwit. This is specified in BIP 143. OP_CHECKSIG on the Bitcoin Cash chain must use this new sighash preimage creation algorithm, but OP_CHECKSIG on Bitcoin uses a different sighash preimage creation algorithm (the original one), so they are incompatible with each other.

The SIGHASH_FORKID is an addition to the sighash type and simply means that the sighash type must have bit 6 set.