Mixing Melee & Ranged
Sometimes a character may be able to attack both in Melee and at Range - for example, a character may have a gun in one hand and a rapier in the other. More complicatedly, a character may have throwing knives in their right hand and have their other hand be open but want to know if they can slash an opponent with their Throwing Knives after throwing one.
One Weapon Fighting or Multi-Weapon Fighting without Bonus Attacks
In these instances, consider every attack used with ROF, regardless of how many the character may make in a round, to reduce their total number of Attacks by 1 - an ROF of 4 or of 1/4 both remove one Melee attack per ROF spent. Conversely, any Attacks used on melee decrease the effective RoF by 1. Thus, a character armed with a musket that fires a shot but only has 1 attack would not be able to use the bayonet attached to it immediately after this. If a character is wielding a sword in their off-hand and a pistol in their main hand but is not gaining bonus attacks from Two-Weapon Fighting and has 3 attacks per round, firing a shot with the pistol only consumed one attack, allowing them to use their sword for two more attacks.
Multi-Weapon Fighting Bonus Attacks
This does not, however, have an effect on bonus attacks received from Two-Weapon or Multi-Weapon Fighting BUT the character must account for these - if the character did not initially state they would be using Two-Weapon Fighting and suffer the penalties on their Ranged attacks, Melee attacks later in the round from Two-Weapon fighting would not be possible.