Yes, good question. I think the difference will show itself in how people act when they think no one is looking - in the case of externally imposed moral codes, there’s a much higher probability that those will be set aside if they interfere with other goals, and if they think no one will know. But if someone acts out of a genuine inner conviction, they aren’t likely to disregard those, irrespective of what circumstances they find themselves in.
It reminds me a little of the situation in the former communist Eastern Bloc - the vast majority of ordinary people externally toed the party line, parroted the right slogans etc, which enabled them to live some semblance of a normal life. But behind closed doors it was a different story - very few actually genuinely believed the ideology, which is why the whole thing just crumbled in the end; there weren’t hundreds of thousands coming out to do their utmost to preserve their beloved systems. That’s the difference between imposing a narrative with fear, versus genuine conviction.