Macrumors (The 27-inch iMac's flash storage is soldered to the logic board and cannot be removed, but for 4TB and 8TB configurations, a flash storage expansion board is attached to a connector on the logic board. The 256GB, 51GBB, 1TB, and 2TB configurations do not have an expansion board and connector, and there are also no SATA connectors on the logic board to support a mechanical HDD.) states that the 4TB and up SSD's have a connector vs being soldered on but one still need to disassemble the machine, not a trivial exercise. For a skilled tech or repair person it is an advantage, for a layman, not so much. RAM, on the other hand is user replaceable even by a klutz like me. And, replacement or brand is irrelevant to the warranty. I put OWC RAM in my MacPro 2013 trashcan and have had a number of AppleCare discussions over the years, none of them asked about whose RAM I had. It appears that the new 2020 iMac can be turned into quite a machine...for a price.