Wasm-GC are abstractions for compiler writers to enable GC dependent languages to run without shipping a GC to run inside the already GC'd browser/Wasm heap and instead just use the browser GC directly.

So yes, Java,C#,etc will work better (If you look at the horrible mess the current C# WASM export generates it basically ships with an inner platform containing a GC), and no, it will explicitly not speak with "javascript" objects (you can keep references to JS objects, but you cannot call JS methods directly).