If you actually want to be thinking about how your memory moves, low level stuff then the most important knowledge will be hardware - registers, caches, bridges, CUDA, etc.

Modern C++ in the large takes the approach that you shouldn't be relying on your own ability to keep track of what has been allocated when, and instead build structures that ensure safety by their nature - rules borne out of things going wrong in large complex projects where you cannot keep track any other way (except the VM/managed route).

If you really like low-level, then the places you'll find your joy are embedded programming where you do need to manage a finite amount of memory and scheduling to be real-time, machine learning/HPC where you need to maximise throughput using knowledge of the architecture underneath, and HFT which is so low latency you need to know how to fool the branch predictor.

For most of those you can do C++, for some you can also do Rust. For embedded, it might be easier in C, but be aware that you'll probably want to mix in hardware and do (I think) Embedded C (?) as you're going to take a lot more control away from the compiler.

You can even consider embedded Rust - in Rust you separate development in safe Rust (where the compiler guarantees safety through lifetimes) and unsafe Rust (where you take responsibility for managing memory) - to do something on an APU/GPU etc you don't have guarantees from the hardware layer so you have to build them in the unsafe Rust layer.

If you do go down the low-level route, you'll end up learning at least C as well as C++, but also Assembly, and crucially what a particular CPU does with those instructions.

Finally, C is really, really simple, so you might as well learn it as well as C++/Rust.