You install these packs just like normal resource packs. Download the zip and put it in your .minecraft/resourcepack folder, you can go to this folder by starting minecraft and going to Options -> Resource Packs and press Open Pack Folder. After you’ve done that in minecraft Options -> Resource Packs press the > on the available resource pack to load it. After this it should be available.

Older resource packs should work on newer versions of minecraft. For example a 1.18.2 resource pack should work on 1.20.4

Godzilla pack by Gibablast:
Adds Kaijus, like but not limited to godzilla

Pack by Ruvy:
Adds animated tails, legs, beaks and more

Packs by Valaron
Adds weapons, armor, hair styles, ears and more

Pack by Nymphh
Adds tails, hair styles, horns, wings and more