While it can use clang as a backend, Nim does not rely upon LLVM support like Zig or Rust (pre-gcc-rust working). Use on embedded devices is fairly popular: https://forum.nim-lang.org/search?q=embedded (or web search).
Latency-wise, for a time, video game programming was a perceived "adoption niche" or maybe "hook" for Nim and games often have stringent frame rendering deadlines. If you are interested in video games, you might appreciate https://github.com/shish/rosettaboy which covers all but Ada in your list with Nim being fastest (on one CPU/version/compiler/etc). Note, however, that cross-PL comparisons are often done by those with much "porting energy" but limited familiarity with any but a few of the PLs. A better way to view it is that "Nim responds well to optimization effort" (like C/Ada/C++/Rust/Zig).
I do not know enough of Zig to compare the complexity, and Nim is indeed not simple. To borrow from the zen of Python, it is complex but not complicated; and most of its complexity is of a kind you can almost entirely ignore until you need it, and when you need it, you're in trouble if your programming language doesn't provide it. e.g. operational transforms, macros, compile time execution. pragmas.