They're not the same. Everett Ross and Thadius Ross have separate identities and storylines in the comics. Their powers, if any, and character arcs are completely different.
The uniqueness of their relationship. Tam and Sheldon are both very different characters. Sheldon is extremely intelligent but socially awkward, while Tam has his own set of qualities. Fanfictions that explore how they interact and complement each other are special. For example, Tam could help Sheldon in social situations that he struggles with, like understanding group dynamics at school.
Perhaps an intelligent and patient psychologist. She could help Sheldon understand his emotions better. Given Sheldon's complex personality, she would need to be very understanding and be able to handle his idiosyncrasies. This type of girlfriend could also introduce Sheldon to the world of human emotions in a more systematic way.
One great Young Sheldon Tam and Sheldon fanfiction could be one where Tam helps Sheldon with a difficult science project at school. Tam might bring in some unique ideas from his own background that Sheldon hadn't considered. Another could be a story about their friendship growing over shared interests in comic books, despite their different personalities.
Since I don't have a lot of information about this specific story, it's hard to say exactly who Mike Ross is. He could be an ordinary person with an interesting personal story that involves some sort of growth or change symbolized by 'big boy pants'.
I'm not sure specifically who 'ann b ross' is just from this phrase. It could be an author. Maybe it's someone who has created works within the realm of 'fantastic fiction' which might include elements like magic, otherworldly beings, or extraordinary adventures.