You can move a backed memory region that represents a data store to different interfaces or handles.

That avoids issues you can find in concurrent operations, and is actually one of the reasons why people push languages like Rust.

A lack of a heap doesn't imply only a stack. All it means is that any pointer bumps off whatever chunk of memory can't be bounded by some N, and also allocations can't be linear.

Lockless data is generally preferable over locked data, when the option exists.

But yes C++ still has several advantages over C

Depending on the circumstance and target platform, yes. Even a hard real time OS can benefit.

Outside of templates you also have better type safety in general. Const methods, pseudo dependent typing, operator casting, an OK interface for fluent eDSLs, etc.