Concealment Confusion / How to use Fog Cloud

[Greenstone.Walker]

You cannot make an attack of opportunity against a target unless you can see them, so a fog cloud dropped on a melee allows people to escape safely without having to take the Disengage action.

Casting fog cloud on your own location and then stepping a few feet sideways means that enemy archers are very unlikely to hit you, since they have to guess your location and then, even if they guess right, attack at disadvantage. This helps you keep up concentration, among other things.

 

[UngeheuerLich]

RAW, you are correct: The advantage and disadvantage cancel out.

Our group house ruled that ranged attacks have disadvantage when attacker and target can't see each other, while melee attacks are by the book.

A good house rule. Especially because I think, that as a ranged combatant you are too far away to be able to distinguish between friend and foe during a battle or locate the exact position without effort.