as the lifelong uncontested regional vice president of the itty bitty titty committee, it is totally worthwhile to look into different methods of measuring bras and totally worthwhile to test out those findings by trying on bras from various retailers in various sizes to see what is comfortable for YOU because there is no one correct way to measure bras and sizing, elasticity, cup shape, etc. are inconsistent between brands and lines.
I 100% know how to "correctly" measure my bra size, but it's not helpful information when band size + cup size doesn't account for where on your chest your tits are set and *even given* correct measuring it's nearly impossible to find the band/cup combo for you *and* adding spacers to the band changes where the cups are set *and* there's probably a disparity between the boobs because there usually is and it's not a big deal your boobs are fine it is the bras that are wrong.
If you're using all sorts of measuring guides and are still having trouble finding bras that fit you the way you want them to, I know it's frustrating and I want to say that A) you are most likely not doing it wrong there is literally no single method that works for everyone B) mass manufactured clothing is just not made to fit every body type and you are probably correct and it is legitimately hard to find something that works (for which I'm sorry, I hope you hit upon a good solution. mine is sports bras with no cups and tank tops with built-in shelf bras).
The second photo is maybe the biggest that my tits have ever looked and I am laying on my side and they are *still* not touching. Where's the bra where I can put spacers in the front because the girls are fighting.
These are teacup tits that nonetheless require the intervention of helpful nighttime elves to construct an adequate harness for, apparently. There are no helpful nighttime elves in my vicinity so the answer is "camisoles and it's not my problem if you can see my nipples."
Also, no, I have never found a dress shirt that fits both my arms and my chest without significant tailoring so the answer is lace-neck tanks with shelf bras and cardigans in environments where I have to present both professional and feminine.
Mass-produced clothing is made to fit averages, if you are outside of the average that is not an indication that you are not wrong for not fitting in the clothing.