I'd just pop them if you haven't already. I'm not sure if they carry over because I popped or traded them, but yeah, as someone said, they aren't really the keys to get through. I only had earned two old souls, but because I had 1 million soul memory, I was able to progress past the Shrine of Winter in my original playthrough. Its likely not solely dependent on you just having the souls in your inventory as much as it it just having a certain amount of souls racked up. And anyways, you'll just end up getting them back on your second playthrough regardless, so no sense in keeping them unless you're planning on not leveling up on your second runthrough. As a side note about NG+ in general though, I don't understand why everyone talks about there being an immense difficulty curve from the original playthrough to NG+. If anything, I've been having an easier time and been progressing at a much faster rate. Something that took me a couple of days to do in my original playthrough was done in one sitting on my second playthrough. No-Mans Wharf was still absolute hell for me though, just less so.