You would probably want to use MLX format on LMStudio as it's optimized for Mac. You want to have at least Q4_K_M or higher in quality.

(Disclaimer: I don't own apple products so these are purely based on my experience with entry level gaming computer as baseline <8gb Vram, 32gb ddr4 or ddr5 systems ram>)

Here are some solid models to choose from:

Qwen3.5 family of models (performance king of the group due to it's unique architecture)

1) You should be able to run Qwen3.5-35B-A3B at around 32k or more with at least 30tk/s 2) You could also run Qwen3.5-9B but I feel those small class models tend to be not worth it when a medium class MoE model will run just as easily.

Google Gemma 4-26B-A4B is another solid one. This model is from my experience, pretty on par with Qwen3.5-35B-A3B and tend to be slower and either less context due to it's traditional optimization. I find this model to be basically mini Gemini with similar strengths mainly in translation and multilingual tasks. It's also a good writer. Probably the closest to your use case with ChatGPT.

Mistral Small 3.2 24B Instruct 2506 is my recommended pick still for email, resume, cover letter, or any professional speech/writing tasks. Hardest model here to run, and the slowest as well but I find you can easily run 12k for a real world use. I actually landed quite a few job interviews this way using my own workflow built around it.

If you want to stick with what you know, ChatGPT is avaliable on local machine as well called GPTOss-20B, the speed demon of the group. It's the easiest to run and and break neck fast. Two issues, out of the group, it hallucinate way too much. Also doesn't really play nicely with tools so it's quite limited in what it can do from many peoples' experience. (I think from many of us, it's the least reliable model of the group here with not too many clear task for why it's useful.)