NNUE is an fascinating and throughly modern approach, just like your Rust choice. Ninny Chess Club doesn't need NNUE to crush human opponents, although I considered it. Instead, I went with standard classical chess engine techniques I remember from Shredder and Crafty days. PeSTO keeps it very fast, of course. Hope you give it a go on "Deadly" level vs. Prodigy. Good luck with GaiaChess.