Cash is mined by ASICs and gold is ASIC-resistant and was created to be mined by videocards (to be sure people have what to mine if ethereum moves to POS finally).
If Eth goes to POS EVER than Zcash will be king and other algorthims before Bitcoin gold.That's possible. But anyway bitcoin gold was created to try to compete in this mining market.
And bitcoin cash was created to try to solve bitcoin's problems and compete with the one
actually bitcoin gold was created so that their developer can make more money quick and out of nowhere. they are the least competent developers of all times. everything is always behind schedule and other third parties did half the important things such as implementing replay protection!
that is why they premined BTG this much.
and bitcoin cash was created mainly to take over the "power" and control over bitcoin development. it was not really to solve anything and increasing the block size did not solve anything either. it just gives the illusion of no problem for a short time because nobody is still using BCH. the blocks are completely empty.