Model reocmmendation for live translation on Iphone 16 Pro

I’m building an iOS app for real-time English ↔ Mandarin Chinese translation on an iPhone 16 Pro Max/A18 Pro chip with 8GB ram.

What small local model would you recommend that can run fully on-device with very low latency, while still being good enough for natural, nuanced conversations rather than basic phrase translation? Ideally I want translation fast enough to feel close to a normal back-and-forth conversation. What would you use? Is this even realistic to do?

thanks