I guess MinGW went its own way using Clang, without GCC counterpart.
It's not that "mingw" itself goes any specific way at all. Mingw is just the headers and libraries (mostly import libraries). Since forever, you can choose to assemble a full mingw toolchain with either GCC or Clang. You can use Clang+binutils, or GCC+LLD, or whichever combination you like. For c++ library you can use libstdc++ or libc++, for base library you can use libgcc or compiler-rt. Any toolchain vendor can decide to build almost whichever combination of them that they like.
llvm-mingw happens to be one such toolchain setup, which uses Clang, LLD, compiler-rt, libunwind, libc++abi, libc++, without any of the corresponding GNU counterparts. These toolchains support both i686, x86_64, armv7 and aarch64. (GCC doesn't support targeting armv7 Windows either, only i686 and x86_64, and the in-progress aarch64 target. There was some sort of support for older ARM for Windows CE though.)