MiniPC to run a LLM w/ voice assistant - Best small LLM?

I'm having a go at building a fully offline, voice-first assistant running locally on a fanless mini PC (4 core Celeron J6412 w/ 16GB DDR4, 512GB SATA SSD, crappy Intel UHD iGPU only) Going to try Ubuntu 24.04, llama.cpp, Python.

Are there any models that might be able to hold a strong persona and stay concise on this class of CPU? Is there a STT for short commands that might work real time on a weak CPU?