Your iPhone 7 has 2 GB of RAM. iOS uses about half of it. All of the other apps must share the remaining 1 GB. Which means that probably no more than 2 or 3 apps are in RAM at the same time, regardless of how many appear in the app switcher (which is just a list of apps that have been run; it is not an indication of what is currently running).
The displays have rounded corners. When measured diagonally as a rectangle, the iPad Pro 12.9‑inch screen is 12.9 inches, the iPad Pro 11‑inch screen is 11 inches, the iPad Air and iPad (10th generation) screens are 10.86 inches, and the iPad mini screen is 8.3 inches. n8wg.