If you're going for just grammar and spelling, Grammarly has been around for ages and doesn't try to rewrite everything. I'm a native speaker and I don't trust any LLM to retain my style because diffing paragraphs or reworking sections is tedious as hell. I'm reeeeeally lazy and the only workflow I am tempted to do is a rough draft from an LLM, a full rewrite from me, and something like Grammarly for small mistakes. Anything over a single iteration feels like pulling teeth because it's never as subtle as you tell it to be. It truly feels like giving a typewriter to monkeys.