> Which still means you have to write your code at least thrice, which is two times more than with a variable length SIMD ISA.

256 and 512 bits are the only reasonable widths. 256 bit AVX2 is what, 13 or 14 years old now.

no. Because Intel is full of absolute idiots, Intel atom didn't support AVX 1 until Gracemont. Tremont is missing AVX1, AVX2, FMA, and basically the rest of X86v3, and shipped in CPUs as recently as 2021 (Jasper Lake).