According to Parsons, after coming out, he was able to more easily do that in his work, which likely helped make Sheldon a more fully realized character as time went on.
For many actors, part of digging into a character (especially one as intriguingly filled with quirks as Sheldon was) is mining your own life for emotional truths that can help you relate to whatever your character is going through.
Not only does Parsons feel that being able to publicly acknowledge that he’s a member of a group that’s remained strong and persevered despite many difficulties has given him “happiness and strength,” but he thinks coming out made him a better actor, as well.