What can you tell from the numbers?
BN, I think we need Jeff, our resident naval architect, to wade in here and give you his answer...but let me mention a few things that may be helpful.
First, I think you are trying to zero in on a one or two discrete characteristics (of a boat''s design) in order to determine qualities that are shaped by a variety of variables. E.g. you are asking about the value of a high B/D ratio when in reality your issue is probably the boat''s ultimate stability at sea, which in turn is going to be determined by a variety of things (form stability, beam, rig, keel type & shape, and how the boat is managed, among others). When we see a modern production boat (several French & U.S. mfgrs. come to my mind...) with a shallow draft keel, a tall rig and a real-world, fully provisioned 30% B/D ratio, I think we all are a bit worried about its capsize potential out in Big Water. But that doesn''t necessarily mean that more ballast is always better. Shopping for a boat for offshore sailing is better done by using a mix of information, including but not limited to numerical design parameters. (So in response to your title for this thread, I would answer: "Some things but not a lot..."
Second, I think you would benefit by doing some selective reading on boat design. It won''t necessarily produce a list of ''good boats'' which will suit your purposes but it will get you to reflect on a wider range of issues and better discern ''good'' from ''bad'' designs. Everyone has their favorites references but here are a few sources I''d encourage you to read:
1. Dave Gerr''s The Nature of Boats; Dave strikes me not only as a knowledgeable sailor & designer, but an artist with the written word.
2. John Neal''s web-based discussion on the characteristics of a good offshore sailing boat, found at www.mahina.com/cruise.html John has sailed over 300,000 offshore miles now and has provided cruising instruction to sailors in the SoPac, Antarctic and Atlantic for several decades and his discussion is about the real-world design and build features of a boat being taken offshore.
3. I would also recommend one of the cruising boat references that integrates a discussion of sailing and cruising with a discussion about boat design and boat features. One good choice IMO is Nigel Calder''s Cruising Handbook, specifically the first few chapters.
Third, some folks will recommend a book that describes a selection of ''good designs'' or good offshore boats (e.g. John Vigor''s Seaworthy Offshore Sailboat) but of course that means you are relying on someone else''s homework rather than your own. Still, the value of such a reference is that you can pick up info on how a boat was built, which can be very instructive.
You asked about narrow beam. While it is just one more variable, it''s true that in general narrower boats can provide a speed advantage, other parameters being equal. While modern offshore boat design has sometimes led to more beam and initial form stability, another track has produced decidedly narrow (B/L) ratios in order to provide faster passage times for a given displacement and therefore boat cost. That was part of the original rationale for the Sundeer yachts from South Africa.