It will affect his health, but only in a good way. It will eliminate the chances of him getting testicular cancer later in life. It will help to stop territorial behaviors like spraying and fighting with other cats. It will improve his overall disposition because he won't be "on the prowl" all the time.
It will not affect his playfullness, vigor or health.
Neutering is castration, by the way. Do you need more details on that?
Let me know if you still have questions.
