Tails is the tallest in Team Sonic, having gone through a pretty massive growth spurt in his teen years.
Tails suffers from intense anxiety due to growing up with two tails, being assaulted for it as a child and still suffering the effects of that trauma. Sonic is his metaphorical rock, and if the two are found together, its a high chance of a high anxiety day.
After the events of Adventure and Adventure 2, Tails had a sudden relapse with his mental health. This caused him to rely heavily on Sonic for quite a while, but with the help of Sonic and his friends, he was pushed to slowly be okay on his own again.
He's currently planning a trip to travel Mobius in the Tornado, alone, for the first time in years.
He housed Gala for a few months after the events of Frontiers. The two of them were able to get along fairly well, even if they were awkward with each other.
I headcanon Tails to be genderfluid, typically using mirrored pronouns (Tails uses what you use!) He's not fussed about figuring out his identity further than that at the moment, that's not the kind of self discovery journey he's on. Girls are kinda cute though, he has to admit it.
The jacket he wears is one he thrifted while shopping with Amy when he was much younger, and smaller. It was too big on him at the time but he loved it too much to not get it. Lucky for him, he grew into it!