In some fanfiction, the spiked combat boots can have a personality of their own. They might 'talk' to Percy in his mind, giving him advice or warnings. This adds an interesting dynamic to the story as Percy has to not only deal with external threats but also with the voice in his boots, which might have its own agenda.
The main difference is quality. Good boots have better quality materials and construction. Cheap boots are made with lower - grade materials. Good boots will last longer and be more comfortable.
In some fanfictions, the spiked combat boots might be a gift from a minor god. They could have special powers like being able to teleport Percy a short distance. So, when he's in a tight spot in a maze or a dangerous battle scene, he can just use the boots to disappear and reappear in a more favorable position.
I'm not sure specifically what 'Cap deage' means. It could be a very specific term, a misspelling, or something relatively unknown. It might be a proper name, a local term in a certain area or a very niche concept.
I don't have enough information to say exactly who Cap'n Kathy is. She could be an original character created by the fan fiction writer. Maybe she's a pirate - the 'cap'n' part could suggest that - who has some connection to the wizarding world of Harry Potter.
The cap man and monkey story is an interesting one. There was this cap man who was traveling around selling his caps. He reached a place near a forest and decided to take a rest under a tree. While he was sleeping, the monkeys in the tree noticed the caps. They climbed down, grabbed the caps, and went back up the tree. When the man woke up, he was confused at first, then saw the monkeys with his caps. He was worried as those caps were his livelihood. But then he remembered that monkeys often mimic human actions. So he took off his own cap and tossed it. The monkeys, being the imitators they are, did the same with the caps they had taken, and the cap man got his caps back.
Knight boots could be matched with all kinds of dresses. The knee-length midi skirt, pleated skirt, and other skirts that fluttered in the wind matched the knight boots very well. The skirt could cover the boots, keeping them warm and light, but also giving them an elegant feeling. In addition, soft knitted skirts and leather skirts were also good choices. If you want to show off the effect, you can choose a pair of knight boots with heels. The combination of knight boots could make people look more high-class, fashionable and slim.