Wi? Oh wi?? I think my wifi is finally dead on my dying iMac

[PeterW]

Umm, a fusion drive is slower than a straight SSD. It was devised when the price of SSDs was very high (as opposed to merely high today).

And opening a 2012 mini is very easy while installing a second drive is involved but not difficult. Watch the OWC video or read the ifixit instructions.