The grey one looks like a pullet. The white one has small streamers on the back of his/her head, as you said s/he stands like a cockerel. S/he doesn’t have any wattles though which means s/he could be a pullet, but his/her comb is in more of a U shape which can sometimes be a sign of a cockerel. For the white one I think I personally am leaning more towards cockerel, but if you think it sounds more like s/he is a pullet then that’s fine. Just so you know everyone here will be making a guess not a guarantee. Silkies are hard to sex and you won’t know for sure unless they lay, or crow.