I think it's less about dressing "to not attract attention," and more about dressing for your body type. Clothes that flatter will always reap better results in the "passing" game. Properly fitted clothing for your body type, in colors that flatter is all that matters (ie Harmony in Dress). I wear 40s/50s attire almost exclusively... I get plenty of attention, but when the clothes fit you well and you carry yourself with confidence its just "Wow, she looks AMAZING." I get the same reactions with blue jeans and a black t-shirt, or a wiggle dress... or a full on swing dress with petticoat... even works with tailored slacks and a basic collared blouse.
Despite what women would have you believe, there's a lot of thought going into what makes their no makeup loungewear look effortless yet flattering. The part that is overlooked is that they have developed their eye to spot their flattering cut/fit at a glance over decades. Like in surgery, in tailoring millimeters are miles.
Drag is more about making your body fit the clothes for a performance. Cross-dressing is about wearing the clothes because it makes them feel good. Passing is all about fitting the clothes to flatter your body. 3 very different goals.
Blending and Passing are also very different ideas. Blending is camouflage to hide in plain sight, Passing is about being yourself in daily life and nobody questioning your gender. You should always dress how you want to see yourself, otherwise what was the point? For me, my style is 1940s and 1950s. And pulling it off successfully is all about Harmony in Dress.