OP:
If you're going to get a 2015-design iMac, this one would be better than either of the 2 you posted above:
https://www.ebay.com/itm/202117459305?siteId=0&AdChoicePreference=true&rmvSB=true
(no financial connection to the seller, just a good deal I saw and saved).
I wouldn't recommend ANY iMac with only a 1tb fusion drive.
These have a -very small- SSD portion, which will quickly "fill up". After it does, the internal platter-based hard drive will slow things down.
Get either a 2tb fusion drive, or a "straight SSD" (even a 256gb will do).