Welcome to the forum.
First, probably any of the boats you mention would sail offshore
. Not familiar with the Standfast and the BR43 would depend on who built the boat (most SA built BR seem to be well made). In general I think most sailors say Beneteaus are better made than Jenneaus.
Keel. I have owned boats with external lead keel bolted on and encapsulated keels. For a cruising boat I prefer the encapsulated design since it eliminates a few maintenance
concerns. With an external keel you do need to make sure the bolts are in good condition and I found that the joint between the keel and the hull
always worked a little and showed a thin line every time I hauled, even though I caulked and sealed it every time. Always made me wonder how much salt water
was seeping into the joint and corroding the keel bolts
where I couldn't see them.
All that being said, plenty of boats have external keels and sail for many years without a problem. If I found the perfect boat I would not scratch it from the list due the that one feature.