I've got the late 2015 with 512GB NVMe SSD, is there anything you'd like me to run for you?
CPU here: https://forums.macrumors.com/threads/early-vs-late-2015-imac-27-5k-side-by-side-benchmark.1931874/
CPU here: https://forums.macrumors.com/threads/early-vs-late-2015-imac-27-5k-side-by-side-benchmark.1931874/