When done right, lowering a vehicle can improve a number of characteristics, including handling, top speed, and aerodynamics. Having a lower center of gravity improves handling by reducing weight shift and the tendency of the vehicle to begin tipping over.
Lowering Methods
The two most common ways of reducing ride height are installing lowering springs or cutting the stock springs. Cutting springs is a much cheaper way to do it, but usually any benefits that would have been gained are lost due to reduced load bearing ability in the spring after being cut. Lowering springs are usually specifically designed for the particular vehicle, and provide much better performance than a cut stock spring. They are usually stiffer as well, to make up for the lost height and for a more sporty driving feel.
Other ways to lower a vehicle include redesigning the suspension and installing smaller wheels. A suspension structure redesign is quite an expensive route to take because it involves a lot of custom fabrication. Smaller wheels also reduce the ride height of the vehicle, but also change other characteristics, including tire/road contact, top speed, acceleration, and visual appearance. Additionally, every inch the tire size is reduced only lowers the vehicle half an inch.
Problems Encountered After Lowering
When lowering a vehicle by replacing or altering the springs, the alignment will be altered, potentially by a lot. Angles like camber, toe, and steering axis incline will likely need to be accounted for.
The following are affiliate links to supplies you may need to adjust camber after lowering
Fixing Camber Angle
On models with struts, a "camber bolt" can be used to bring camber back into a reasonable position.
How To Use Camber Bolts
In this Cars Simplified video (published on March 30th, 2019), Steve will guide you through the theory behind camber bolts.