Sorry, but you're kind of fucked on the t-shirt front.
As someone who used to live in fitted Ts, I actually had to buy a serger and learn how to use it in order to get a t-shirt that fit the way they used to.
I've since switched to merino wool t-shirts anyway. Icebreaker makes some nicely cut ones that aren't boxy or long. They're about $100/shirt though.
As for underwear, I buy a cotton kind from La Senza that has thin edges and a thick band of ultra comfortable lace at the top, so nothing digs in and looks virtually seamless under clothes. I can't wear any synthetic fiber underwear, so the usual seamless are a no-go for me.
As for bras, well, that's 100% personal. I'm a specialty size, so I have that issue, but it also means that no bra lasts very long, so I can't even fathom a bra lasting 10 years of regular wear.
Even then, I've pretty much given up on real bras and mostly wear Puma sports bras that I buy at Costco in a 2 pack.
Now whenever I wear my $250 underwire, I can't understand how I used to tolerate it 12 hrs a day!!!
Overall though, I've found the most consistent source of well priced, decent quality clothes to be the Costco products that are made in Canada. Unfortunately, they're all too big for me now, so I don't buy them anymore because it's not worth the time and energy I have to put in to tailor them.