Two part question:
1) Is phenylephrine the only vasopressor that constricts blood vessels on the venous side and therefore cause a DIRECT preload increase to the right ventricle?

As far as a cascade effect, phenylephrine also causes an increase of the preload of the right ventricle through vasoconstriction of capillaries on the arterial side which increases (inc) SVR. Inc SVR in turn inc PAWP which in turn eventually inc RVSWI which stretches the sarcomeres (ie. in RV preload).

2) Is it then also true that ALL vasoconsrictors (ie levophed) cause a inc in RV preload?