You could carry around a portable display, but that might be a bit of an overkill in terms of cost and bulk. Unlike a display, a portable keyboard is lighter and often smaller than the laptop itself. Modern wireless keyboards have almost no lag, have nice mechanical keys with replaceable keycaps, etc.
Working away from a stationary setup, I consider a separate keyboard a must—and particularly a wireless keyboard, since the one thing that reliably breaks on every laptop is physical I/O, especially USB/USB-C ports (and every time plugging/unplugging another accessory brings that closer).
Working with a stationary setup you have a detached keyboard anyway, and if it’s wired you don’t really need to unplug it, like, ever, so a wireless keyboard loses a lot of its advantages—though if you have a really large screen and have a lot of leeway for moving your chair around for comfortable work not having cables get in the way might be nice as well.