The specific scenario:
I have a fighter character with Quick Draw feat and Sidestep Charge feat, and this fighter charges to a enemy wizard with his longsword two-handed to utilize his 1.5 * STR DMG bonus.
And then, after his charge attack, he switches his longsword to one-handed (IDK what action this is) and draws a whip as a free action (Quick Draw) to prevent this wizard from escaping his AoO via a 5-feet-step. (With a reach weapon, now he can threaten 10 feet.) After doing so, he ends his turn.
But later in the same round, an enemy barbarian charges at this fighter. As a reaction to this attack, the fighter instantly triggers his Sidestep Charge feat and gains +4 dodge AC against this attack. After successfully avoiding this charge, based on the feat's effect, he gains a chance to make an AoO against this barbarian.
To utilize his STR DMG bonus again, he chooses to drop his whip (as a free action), switch his longsword back to two-handed (IDK what action this is) and make his AoO.
And right after this AoO, he draws another whip (as a free action), switches his longsword to one-handed again (IDK what action this is), and regains his threat range.
Are these actions possible? Should I count hand-switching as a free action, just like dropping an item?
PS. Another extreme scenario if it is a free action:
As a fighter with Improved Unarmed Attack and Two-Weapon Fighting feat, I can make a full-round attack with my longsword two-handed as my main attack and my left empty hand as my off-hand attack by constantly switching between one-handed and two-handed between every single attack during my full-attack action.