Regarding BD and other foam liners, is it true that they are higher volume than the stock liners?
No. Not in my experience, and in the experience of four family members and probably a dozen close friends. And in my boot guy who is a good friend and foams at least 100 pairs a season. Also sells ZipFit, Intuition, and had two other foam lines before going all in with BD. None of us have any affiliation with BD.
I'm in a pretty tight shell fit. I would bet that some "fitters" would start buy sizing me up. Wrong way to go. My daughter and daughter in law are in a very tight shell fit {but positively roomy compared to many, many years in a plug. My son has an 11E foot in a 305mm Doberman that has a lot of work done to it. So all tight. All in various liners. All made by BD, as they have a couple of friends for whom they are a preferred go to. Plenty of room for the liners. Great fit. Nice mix of comfort and performance. They just work.
Are they warmer? I think so, and only because of the fact that they eliminate an pressure points, and your circulation tends to be good. It's got nothing, IME, to do with the actual foam, the volume of the liner, etc. My wife had hers fitted to accomdate her heated socks. No heat for the rest of us. We have a lot of data in them and they have not degraded, stretched, etc. One pair has about 300 days on it. I'm guessing they they may go to 400. That's pretty good, until compared to a few ZipFits that I know are edging up on 1000.
My brother has a foam Head liner, and is similarly "sold". Loves them. There are a lot of good foam liners out there.
Have never heard a boot guy, or lady, experienced with a foam liner and foaming process suggest that they have too much volume compared to any stock liner, let alone an RS liner.
Yes, a few changes to the technology since your last pair of Lange's. Enjoy the new boots!