None of the above.
The 2011 is out because it's not compatible with current and future OS (too bad—it's the easiest iMac to upgrade).
It's ridiculous to buy a 5 year old or older Mac with a spinning HD—that includes all fusion drives. They're old and wearing out unless you plan to replace the HHD as soon as you get it.
Either buy a newer Mac with an SSD only or, if you get a great deal on an older one, plan on replacing the spinners with an SSD. It's not hard to do and if you don't want to, there are plenty of experienced Mac techs who can.
The 2012–2017 27" have a socket for a blade and an SATA bus for an SSD. A 2T SSD will run you $300 and you can get a 4T under $800. A 1T is well under $200 these days.
BTW, there's no such thing as an "early 2012". That's the 2011.