Depends on your RAM (main + GPU), but assuming 32GB total: Qwen 3.6 35B A3B for coding support, Gemma 4 26B for general stuff. The LM Studio app curates a list of recommended models that will run well in it and makes it easy to run them.

Mind you, what I like most about local models is their limitations, because it turns out closed models have limitations of the same nature, just with quite a bit more runway; and becoming aware of those limitations is valuable.