Any filter that runs outside the tank is called an external filter. This includes canister and hang on the back filters. I would recommend an external canister filter like the Jebo 819, Fluvals and Eheim types. These usually come with media in them, special ceramic noodles which have a very large porous surface area excellent for growing the good bacteria.
We found the Jebo very easy to set up, runs silently, and rarely needs cleaning. Our Fluvals clog up regularly and are noisier, and our Eheim was a dud from the start (but that is just the wet'dry model - NEVER BUY ONE! I understand all other Eheims are excellent, although a lot more expensive than the rest. These canister filters have spray bars to return the water to the tank so spread the flow evenly along the surface. To lessen the flow you can turn the bars so the holes face towards the back of the tank so lessen the flow if required.
You do not need to worry about the cords getting wet unless they hang in such a way that water can run down them into the electrical socket.
200L doesn't sound big enough for all the fish you want though.