I bought the iMac I’m on now in 2015, it’s a 27" 512gb SSD and i7 with 8gb of RAM (yes I know, not much!). But I have to say it’s been a fantastic machine. The SSD makes all the difference. The machine is still snappy/fast and been really reliable. I say this because when I bought it I remember spending about $3k on it. The new iMacs with say a 1TB SSD, 16gb RAM, i7 10th gen/etc come to about $5k. But then they are really reliable and solid and perform so well.
I was interested to see that the front facing camera has finally gone up to a 1080p and YouTubers are saying that in some tests, the 2020 iMac runs faster than the iMac Pro.
On the downside, it surprises me they still only have 2 Thunderbolt 3 ports on the top end flagship iMac, when all the MBPs have 4, they have 4 USBs when you could live with just two. But they still have the SD card slot and 3.5mm jack so not all lost.
RAM is horrifically expensive, I would buy it now with base RAM and just buy my own and add it in, thankfully they do offer user upgradable RAM still.
Anyway just a few random thoughts from me.