Ranking inside it is decided by relevance, distance and prominence. Distance is fixed by where the searcher is standing, which is why results change street by street and why checking your position from your office tells you almost nothing. The two levers you control are how accurately your profile describes what you do, and how well known the business is.
The pack and the organic results are two separate result sets with shared but distinct signals. A business can dominate the pack and be invisible organically, or the reverse. Entering the pack at all is worth more than climbing within it: the drop from third place to unranked is far steeper than the gap between first and third.