"But Atoms are conceivable - they work as a model, but we can also imagine how to fit into the reality that we experience."

"Quantum Mechanics is a model that fits experiment results very well, but is very hard to conceive of."

These two statements stand in contradiction. Atoms only work as a model if quantum mechanics holds. In a non-quantum world, electrons collapse into a nucleus, shedding electromagnetic radiation and lowering their energy as they do so. That's also necessary to understand why neon signs have their colors.

More broadly, if you want to compare one scientific theory to another and contrast their "realness" you have to take quantum mechanics along with your atomic theory.