different username for commit and github interaction
Solution 1:
The user.name option that you set for Git commit authorship isn't a username at all. It is just a plain old name. (Most people will likely use their real name or something similar.)
So when GitHub wants to display a username, it doesn't look at the author's name at all. It only looks at the author's email address and finds the corresponding GitHub account whose profile has that address.
(You can manage the addresses associated with your GitHub at Settings → Emails.)