EVE is personally my favorite SIMD library in any programming language. It's the only one I've tried that provides masked lane operations in a declarative style, aside from SPMD languages like CUDA or OpenMP. The [] syntax for that is admittedly pretty exotic C++, but I think the usefulness of the feature is worth it. I wish the documentation was better, though. When I first started, I struggled to figure out how to simply make a 4-lane float vector that I can pass into shaders, because almost all of the examples are written for the "wide" native-SIMD size.