I have been using a 15 inches laptop for coding for 4 years now and splitting the screen whether in vim or having two windows next to each other does not make for a great experience. Rather than buying a separate screen and having one more thing to manage I remapped Super + J and Super + K in Cinnamon to just switch windows instantly. Sometimes I even use Super + $number to get to a specific window. I think it works fine and it's more resilient: I can code when I don't have an extra screen