Late reply, but the Baxter and Derek DLC works just like Cove's - you get to chose whether or not you are attracted to them. You can play their dlcs and just be friends; however Cove isn't in a majority of their dlcs as it's centeric to their characters. There is more I can say but that'd be a spoiler, but basically if you only want more Cove content; then you might not be the biggest fan of the other dlcs. (However I will say that personally I find the other romancable's dlc quite fun).