Which model has better CPU-performance: iMac MMQA2HN/A or Mac mini MRTR2HN/A?
The iMac in your screenshot comes with the Intel i5-7360U CPU. The Mac Mini comes with the i3-8100B CPU.

If you look at the PassMark benchmark, the i5-7360U CPU benchmarks at 5823 passmarks multi-threaded and 2047 single-threaded. If you look at the Geekbench benchmark, the i5-7360 CPU benchmarks approx. 9075 multi-threaded and 4375 single-threaded.

In comparison the i3-8100B CPU benchmarks at 8431 passmarks multi-threaded and 2172 passmarked single-threaded. For Geekbench the numbers are approx. 14.000 multi-threaded and 4700 single-threaded.

There could be an obscure corner case, but I would expect the Mac Mini to have the best CPU performance in almost any case. According to the benchmarks, you would expect it to be approx. 40-50% faster, when running a multi-threaded workload (i.e. running more than one app at the same time, or running an app that is multi-threaded in itself). Note that this number may vary wildly depending on what exactly you're doing with it. As the i3-8100B is a newer generation and has a higher frequency memory bus, I would expect there to be almost no corner cases, if any at all.