The only thing that seems 'weird' to me is that anybody should actually be bothered by what others might think if they tuck their T-shirt into their jeans.
When I was your age (about 40 years ago) all of my friends wore sweatshirts, T-shirts, jeans and trainers but I always wore a collar and tie, with a sports jacket, slacks and formal shoes. I didn't even own a pair of jeans, or a pair of trainers (other than for playing sport in) until I was over 40. These days, now that I'm in my 60s, I find that many of my friends are wearing formal clothing, whereas I nearly always wear polo shirts, jeans and trainers. (I've only ever owned a handful of T-shirts in my life. I prefer shirts with collars, such as polo shirts or rugby shirts).
So I probably qualify as 'odd' (or even 'weird', if you like) in sartorial terms but I wore what I felt most comfortable in when I was in my 20s and I still wear what I feel most comfortable in now. I suggest that you should simply do the same.