1. How do I figure out which size to order?
Sizing here uses letters rather than numbers, running from XS up to 5XL, and there's a Size Chart plus a Size & Fit Guide on hand to help translate that from more standard sizing. Using the "Size & Fit Guide" and "Calculate Size" tools will get you the most accurate result, and if you're torn between two options, it's generally worth going with the larger one.
2. Is this a comfortable, practical option for wearing every day?
It is. Without any underwire involved, the Adjustable Wire Free Shaper Bra (Cups A-FF) + FREE Bra Extender relies instead on breathable, stretchy fabric, wide straps that won't dig in, a seamless finish, and a moderate level of shaping — which altogether makes it a solid choice for daily wear, lounging around, travel, or simply long stretches on your feet.
3. Does it show through T-shirts, and what's the best shade for a nude look?
Underneath clothing, it's meant to lie flat and seamless, cutting down on any visible lines or bulging. Beige is your nude/skin-tone pick and works best under lighter colours, Black is suited to darker tops, and White is there for lighter layers — though if invisibility is the main goal, Beige comes closest to matching a neutral skin tone.