I believe you can turn off the GC for Nim. Then you're just limited to libraries that don't rely on the GC, and fully manual memory management.
For example:
proc printf(formatstr: cstring) {.header: "<stdio.h>", importc: "printf", varargs.}
I'd be interested in seeing a comparison of higher level language features rather than performance (which is generally a result of data structure choices, etc). Stuff like package managers, concurrency primitives, cross compiler support, memory management, and general syntax.