Whether 2 Macs should be connected depends entirely on what it is that you hope to accomplish by doing that.
And in order for two Mac minis to share a single display, the display will have to have multiple inputs so each Mac can be connected, e.g. multiple HDMI ports. Otherwise, additional hardware would be required; some type of monitor switch.
Two Macs can be connected together via networking in order to share files and storage, but that is not a common configuration for the average home user.
Most users have a single Mac connected to a display. Many homes have a single Mac connected to a single display and are set up to take advantage of the Mac's multiple user features, whereby each user gets their own user account on the computer.
• What is it, exactly, that you would like to achieve by connecting two Mac mini computers together?