There are a couple of different accepted theories, both of which suggest a practical purpose. One is that they were meant to protect the backside of riders...riders cannot pivot at the waist very well to protect themselves because their hips are grounded by the way that their legs sit against the horse. However, many believe that the wings were designed to make a lot of noise--either to spook enemy horses who were not accustomed to such a racket or because it made the cavalry seem a lot bigger than it actually was...basically, just to intimidate.
As far as riding goes...speaking as an equestrian, I can imagine that they may have been a challenge to ride with...equestrians rarely sit in the saddle; we actually are mostly standing with a lot of weight in our dropped heels. It is a balancing act to begin with, esp. at speed, and even riding with a backpack changes how you move with the horse. It seems as though there would be a learning curve for learning how to ride with them.

hi! you might find some additional information in these related posts:

Did Hussars actually wear wings?

Did the Polish/Lithuanian Winged Hussars wear their "wings" in battle? What was the origin of them?

What made the Polish Hussars so effective?