A marriage of a Catholic to a non-Catholic isn’t sacramental, but it can be valid, even if it is entered into after the Catholic party was baptised into the Church. (In that case, the Catholic has to have permission from the bishop and follow the conditions for marriage between a Catholic and an unbaptised person.) A marriage outside the Church between two Christians not bound by canon law would be considered valid and sacramental, under normal circumstances.
As for the validity of the marriage of a new Catholic who married a person outside the faith before his or her baptism, that depends on whether the non-Catholic spouse is willing to remain married and let the Catholic practice his or her faith in peace. If the unbaptised non-Catholic doesn’t want to remain married or doesn’t allow the Catholic to practice the faith, the marriage can be dissolved and still leave the Catholic party free to marry again. As far as I know, though, the Catholic is bound to stay in the marriage until the non-Catholic either asks for a divorce or else stands in the way of the Catholic’s practice of the faith.
I hope that helps. I’m open to correction, as that is my understanding of it. I hope this is an issue of purely theoretical importance to you, too. If not, please talk to a priest about the exact situation.