Please recommend memory sticks

I plan to buy the latest iMac in the near future. There are the following considerations 1. Is it a good date to buy, because I seem to have seen a post saying that a new iMac will be released, removing the large bezel and removing the fusion hard disk, but I originally planned to upgrade the hard disk to full SSD when I bought it. 2. Memory: I plan to buy an 8G one, and then buy 16 ❎ 4 memory modules and replace them myself. * Do you have any recommendations? *