The top cap and plug are primarily present to set the preload on the headset bearings. Any of the ones you mentioned will work.

The plug needs to be tight enough to resist the upward pull of the bolt passing through the top cap so you can generate a compression force by drawing the fork upwards. Neither is structural, once the stem is tightened in position the top cap is mostly cosmetic, though it could keep things together should your headset become really loose.

-j