Is the best MacBook Pro 13" (2020) more powerful than the best Mac Mini (2020)?

Well, I can't really tell you what to choose. That has to be your decision. If you have lots of open windows, then either the MBP or Mini would be suitable. The MBP would provide the added feature of having two displays, whereas, there would be only one display with the Mini. The Mini has a 6-core i7 vs the MBPs 4-core i5 at a lower clock speed. The MBP does add the feature of portability which the Mini does not. They both have only modestly different integral GPUs. The Mini should outperform the MBP. Personally, I don't consider either to be true desktop replacements, but many, many users do treat their laptops as desktops. So, who am I to argue. Not my cup of coffee but that's just me. The new Mini does have desktop-like specs.

You pretty much have all the specs to compare with your needs. Make a pros and cons evaluation sheet for each to help identify which seems better suited to your wants and needs.

The MBA uses a 10th generation Intel processor which may be faster than the 8th generation process, ceteris paribus. The MBP has faster RAM than the Mini. The Mini has a nearly 50% faster clock speed than the MBP. I'm guessing but the Mini probably outperforms the MBP in terms of raw processor speed. But we don't know what sort of work you do or how suited either of these models would be for your work. Do you need CPU speed, graphics speed?

The Mini is not portable. If you are going for a Desktop model, then skip over the Mini and go directly to the iMac.