The Custom Camera views have exactly ZERO impact on performances per se.
However, since you are generally looking at vehicles from close range, the highest resolution textures are being loaded so, if your card is a bit weak and/or your settings are too high and/or you have many addons installed that use texture memory, you might notice some fps loss, but that's not due to the Camera views, just the fact then when an object is seen from a closer distance, the texture loaded are the highest quality ones.