Why the 30 percent range is strong
A 30 to 35 percent attack keeps most of your troops at home while still claiming enough land to raise your future population cap. That balance is why many map-painting players treat it as the default opening rhythm.
The exact best setting depends on terrain, defense posts, and whether you are attacking neutral land or a protected player border.
When to raise or lower the ratio
Lower the ratio when you are near a hostile border, crossing mountains, or trying to keep your troop count stable. Raise it only when the target is weak, your interest is capped, or a missile has opened a temporary breach.
A full 100 percent attack is rarely a normal expansion tool. It can work as a final all-in, but it usually leaves you unable to recover.