Think a bit about the “old school” games you like to play. Home console games — those that connect to your TV — have a horizontal screen orientation. But in arcades, many games took advantage of a vertical screen.
Cupcade can use either a horizontal or vertical screen orientation, but this must be decided early on. It can be changed later, but this is a non-trivial operation; you’ll need to dismantle and reassemble the whole thing.
There are also three different ways the controls can be arranged…but again, this is a commitment and a fair bit of work to change later.
Therefore: think ahead about which game(s) you’re most likely to play. Maybe test them out on the Raspberry Pi before assembling the whole kit around it. Determine which perform acceptably with the emulator and look good on the screen…then choose a display and control combination that works well for the most (or most desirable) games from your list. Others can still be played, they’re just less than optimal.
This basic joystick-and-two-buttons combo covers a vast number of classic arcade games. You can optionally plug in a USB keyboard for anything more complex.