Pikmin by default remain as throwable items in your inventory, depending on where and how you throw them they'll perform different actions. There are two different throw modes. default and follow. Follow mode is active when you aim at nearby blocks with no entities in the middle, otherwise, you'll be in default mode, The mode you throw the Pikmin in is indicated by a text hint over your hotbar.
Each mode changes how Pikmin behave when thrown, but there are some common behaviors Pikmin always have besides how you throw them:

-Thrown Pikmin can be called back at your inventory by using the Pikmin whistle (Crafted with an iron ingot and iron nugget)

-Most Pikmin can't swim and will drown in any puddle, they'll try to avoid water and will try to return to the player if they start to drown but can barely move so they might need help

-Pikmin slowly regenerates health over time

-Pikmin will run away from entities about to explode (creepers for example) or whatever they were attacking if their HP drops below 4.

-Pikmin panic and run around like crazy when they are burning, poisoned, or get the whiter effect; calling them with the whistle will stop this.

These behaviors are always present on all Pikmin and override most other tasks and activities while active.

Throw Modes:

§dPikmin Storage Controls (Without Interface)§r

Unless thrown to specific things, Pikmin thrown this way will seck and attack the nearest non-pikmin entity, If there's no entity to attack or they defeat their target they'll search and pick up a nearby item, and then return to the player and enter their inventory, alongside any item they a carrying, Pikmin will also return to the player if:

-The Pikmin stays without a valid task for a few seconds or finishes it.

-Their hp drops below 4

-Any other valid case mentioned above occur

By aiming at and hitting specific objectives directly Pikmin will perform and prioritize certain tasks:

-Item: Pikmin will pick up the item and nearby items they can stack it with, returning seconds later bringing the items with them

-Entity: When a Pikmin is thrown and hits an entity they latch onto it, They won't be able to be damaged by regular attacks and will start dealing damage ignoring invincibility frames, Stacking more increases the damage, Pikmin can be shaken off if the entity moves vertically (Flying, jumping or falling), or they get attacked, they can be shaken off, causing them to fall and continue attacking like normal, but now vulnerable to attacks. Pikmin will also fall off when called by the player, entering the water, or panicking, but won't be thrown away.

-Harvestable non-full block: When Pikmin are thrown to crops, sugarcane, grass, bamboo, nether wart, or similar, they'll start breaking all nearby plants of the same type and collect the drops they can carry, They'll return to the player once they can't harvest more being that they can't find more or they can't reach the plants. 
Pikmin can harvest almost all plants and fungi, mushrooms, grass, nether roots, warped and crimson fungus, bamboo, sugar cane, drip leaves, and more, exceptions are full solid blocks like wood, pumpkins, or melons if the block to harvest has growth stages like crops or nether wart, they'll only harvest the fully grown ones to avoid any loses.

Using default mode Pikmin can help you to save time on simple mundane tasks, and quickly collect far away items or non-clustered drops, kill animals for food, harvest some resources, or defeat hostile mobs if you have enough Pikmin.
2 to 4 are Pikmin capable of defeating zombies, skeletons, and spiders on their own, but putting your part by aiming well so your Pikmin can latch onto the enemy and call them back when endangered or shaken off to throw them again, you can defeat most enemies very quickly and efficiently.

§dFollow Mode§r
	
When thrown on follow mode, Pikmin won't do anything immediately and won't return unless called by a whistle or drowning. Instead, they'll follow you around, attacking whatever you hit or hits you,  on top of that they'll also attack hostile mobs that target you before they can touch you but ignore those that aren't currently targeting (calm zombie pigling for example), and even more, they'll collect and deposit in your inventory any nearby items non-stop without the need of any command from your part. To Pikmin return following your inventory, you can either call them all with your whistle or sneak and interact with one to take it.

Follow mode is more useful for support on certain tasks that require your constant action, like mining trips or chopping down wood, instead of having to constantly throw Pikmin at specific items, making some Pikmin follow you so they collect all automatically can both save you time and increase your gains since it will be less likely you'll forget something, basically being a more efficient and portable version of an allay. 
On top of that, Pikmin is more than capable of dealing with random undead and spiders, saving you the hassle of the fight, even more, they can save you from creepers trying to sneak attack you, getting their agro and kitting the explosion, giving you better chances to either run with your squad or just kill it.

§dLost Pikmin§r

The last thing you need to know about Pikmin behavior is lost Pikmin, Pikmin can only be in item form inside a container, if they would exit the container as an item, being because they were dropped by a player, a chest being broken or similar, they return to being entities instead and are considered "Lost", lost Pikmin just wander around until either any player calls then with a whistle, or they find and enter an onion of their color.
