I've had good results rating Fuji ProH at 100 and getting the lab to develop it normally as if it was shot at 400. It has really nice pastel tones (if you like that!). When I've overexposed Portra it goes more yellow, so I would stick with box speed, or maybe overexposing by a half stop at most.

If you shot either at 1600 then you would be underexposing it, and it won't look very good (especially the 400H) so let the lab know that you shot it at 1600 and want it push processed. I haven't shot Portra 400 at 1600 but believe it fares better than 400H if it is underexposed.