Your requirements on those two fronts are key. Interfacing a computer keyboard to an Arduino is difficult and expensive (as you need a USB host shield/module). A small B&W OLED display or character LCD demands very little from the controlling hardware, while a color TFT LCD is awkward to drive from most Arduinos due to the comparatively large amount of data involved.
If you need a good display and a computer keyboard, you may be looking more at a raspberry pi project - as those can natively interface with keyboards and fullsized displays - at the price of being less ideal for interacting directly with other devices.
If a simple keypad and character LCD are appropriate, almost any Arduino will work - Uno/Nano/Pro Mini would be the default choice. Uno is bulkier and more costly, but somewhat easier to work with (particularly if you prefer shields over modules); nano and pro mini are smaller and cheaper (but code-compatible) versions.