Yes. That's not changed. All NIFs (regular or dirty ones) are executed directly in the context of the VM. A safe option would be a port - a regular program where you communicate through stdin/stdout. Ports allow representing such program (running in a separate OS process) as something equivalent to a native Erlang process.

There's also work on supporting writing NIFs in Rust, which gives some degree of additional safety. The relevant project would be: https://github.com/hansihe/rustler

Yes. For such cases, you'll want to instead use a C-Node or a Port program to interface with the C code.