The newest Mac Mini shares the same processors as the current iMac (21 in) and some of the same processors as the 27in version...and has user upgradeable RAM. It's not in the same league as the iMac Pro, but it's def comes close if not surpasses an iMac these days, and a non-upgraded iMac still ships with a spinning disc, where as the non-upgraded Mini's ship with SSDs...
It doesn't come close to an iMac or an iMac Pro.