Yes. Explicit control of memory is one of the big reasons C++ wins for high performance realtime applications like games.

True as far as it goes. Modern GC can mostly be done concurrently (it's only heap compaction that requires stopping the world). Fully pauseless GC is very much possible (see e.g. Azul C4), as are e.g. architectures involving multiple short-lived processes with individual heaps. Even without that, it's often possible to do a relatively small amount of manual work to do the things that require pausing only at appropriate times.

Modern C# allows you to define a code path where GC is not allowed to run. I'm not sure if unity allows for this.

I'm also not sure about the new c# -> to native compilers coming out.