It's my understanding that Carbon will create wrapper Carbon classes around C++ classes and convert data back and forth between C++ types and Carbon types at the interface boundary when necessary.

Not really, Herb Sutter tries to sell cpp2 as "Typescript for C++", or "Kotlin for C++", while ignoring that Typescript doesn't add anything to JavaScript besides types, they did some mistakes on the early days not following up on this, but backtracked and now Typescript is basically a linter/transpiler.

Whereas while Kotlin used the Java ecosystem to bootstrap itself, it is clear that by now JetBrains rather wants to build their own Kotlin ecosystem, just like C++ and Objective-C took their own path after being plain translators into C.