How many different brands have you tried?
My first bib shorts were dhb ones and they fitted right everywhere, but were a bit short in the bib strap department, so it always felt like they were pulling on my shoulders.
My latest favourite bib shorts are Lusso ones and once you’ve got them on and on the bike, you cannot feel the bib part at all. You can feel them a little bit when off the bike, but that’s presumably because you are stretched out a bit more.
I’ve also tried some more dhb ones and they are fine, so either my spine has got a bit shorter or the bibs on these ones are a bit longer than the original ones I had.