I need exhaust options for my F4 Resto-Mod bike.

Ide like to do some super shorty exhaust that just peaks out from underneath the footpeg, or a megaphone exhaust.

Having looked at megaphones briefly, whats the difference between a megaphone and a fancy exhaust tip?
Megaphones have no baffeling in them?
What keeps the back pressure up?
Are these an option for carburated bikes?