GDDR6X is faster memory than GDDR6. It has more bandwidth, and consumes more power too, so it gets hot. Only the 3090 and 3080 have it.
GA10# are the technical names of the Ampere chips. The 3090 and 3080 have the GA102, the 3070 has the GA104, the 3060 will likely have the GA106, and if there's something like a 3050 then the GA107.
It's a naming scheme they have used before with other letters, but always the numbers starting at 102, which is reserved for the biggest chip. The farthest away from 102, the smaller it gets.