Good guide ! less than 20 minutes to change the battery, cleaning the interior included !!
Same as the other comments, in my iMac 27” retina 2015, the WiFi/Bluetooth board is a bit longer and the 4 coax cables are fixed by 2 T5 screws…
In my iMac 27” retina 2015 all screws are T8.
There is also an another T8 screw between the left and central “orange” on bottom of the CPU board