The iPhone now has four variants for the mainstay 12: 12 mini, 12, 12 Pro and 12 Pro Max. The technical differences are relatively small, and much of the consideration boils down to the phone size you prefer.
The Pro’s have lidar, 6 GB RAM, and three lenses. On the normal Pro the extra lens is 52mm, on the Pro Max 65mm with better stabilization. The Pro Max also has a better 26mm lens, adding roughly half a stop more light gathering. This gives three levels of camera performance, with the base level already great for most casual shots. If you want more, you might want to consider something like the RX100 VII, which is not too heavy, and complements the phone quite nicely.
Unfortunately, the Pro models have worse materials in their design: the steel bands add to the weight, non glossy backs make them more difficult to hold, and the color choices are boring.
The main difference really is the size: the Max is too large for one handed operation, the middle size is kind of OK for men, and the mini is the best one. Without the margins, the mini has 15% more screen than the 2nd gen SE, and this is sufficient, especially if you have an iPad as well.
Personally, I like having the 52mm enough that I am willing to compromise on size to get the Pro, but it is not really what I want: camera system of the Pro, size of the mini, but about 2-3mm thicker to accommodate a larger battery and to hide the camera bump.
PS: After a month the 12 Pro still feels too large and heavy. Just enough to irritate me, not enough to dump the phone. It affirms that the phone I really want is the 12 Pro mini outlined above.