Also: 2-player rpgs don't need to be 1-shots! Two is in fact the player count that is -easiest- to arrange repeat sessions for (aside from solo games ofc).
And because 1-on-1 roleplaying is already -very- intimate as an experience, I really don't think you should be usually designing to amplify emotional intensity but should instead be designing to channel & defuse the natural tension.
My best 2-player rpg experiences have been from hacking normal games to work with 1 gm and 1 pc.