The answers you seek may not be the ones you want, but we'll help break down the different types of air filters you can get for your car and what's best.
One of the cheapest and easiest modifications that people do to their cars is to change the intake and air filter for the engine - which basically is supposed to help the engine get more air and breathe a little better. The idea is that a better filter will be able to protect your engine from all the nasty microscopic particulates in the air (which can damage your engine) while providing better airflow. There are three kinds of air filters to pick from, and we'll help explain the advantages and disadvantages of each - as well as tell you which is the best for your vehicle.
This is the most basic type of air filter for your car because it's the type that your car generally will come with. Most, if not all manufacturers will use a panel type filter as shown above, and the material will usually be a special kind of paper that is folded in an accordion shape. The reason for the folding is that the shape increases the surface of the area by fifty times that of the opening, allowing for plenty of filtration without really impeding flow. These filters will sit in the airbox that sends air to the intake of either the turbocharger or directly to the engine of your car.
Perhaps one of the most commonly available and widely produced aftermarket filter replacements are in the panel shape, and are usually designed to be drop-in replacements. There are many different options out there that tout better filtration or better flow, but one of the most well known filter manufacturers is K&N out of the good old USA. Their filters have been empirically proven to improve power and torque outputs of an engine, and the added advantage is that they are serviceable by cleaning and re-oiling so you don't need to replace them. You can see from the photo that the filtration element is a little more complex than OEM.
Ah, we come to one of the most controversial topics when it comes to filters. The open pod filter, as it's more widely known, is a type of filter that completely replaces the standard airbox found on your engine. Gone is that little plastic box in which your standard filter element sits, and you will usually have a form of pipe that connects from the throttle body directly to this mushroom or cone-shaped filter. In concept, these filters look cool and also look like they would flow more air.
In practice, it's not that simple. These filter elements can be physically larger and therefore allow better flow, but the difficulty lies in making sure good quality air enters the air filter, to begin with. The engine bay is a very hot place, and unlike an airbox and panel filter setup, the pod filter is more likely to take in a lot of hot air that translates to less power (we can go over this another day). To make proper use of a pod filter, you need to ensure that cold air gets to it. What is indisputable is that open pod air filters sound undeniably better with throaty induction noises whenever you put your foot down.
Well, the tricky thing is that over time, manufacturers have vastly improved their standard panel filters that you find in their cars to the point where they are pretty much on par with whatever the aftermarket can offer - but it still doesn't hurt to try it out for yourself and see. If you're not chasing every last horsepower, we recommend you just stick with whatever the manufacturer put in the car to begin with, or a certified OEM replacement.