Question: what is the difference between ram 1rx16 vs 1rx8?
Answer: The difference is the memory density. 1Rx16 is lower density memory than 1Rx8. 1Rx16 memory is very hard to find, and since the 8 GB chip is 1Rx8 and you want to add another one, that is what you should look for. Here is the crucial memory report which has compatible memory for your notebook.