I had to think about it for a sec but I can’t recall the plate ever interfering with my ability to shoulder and accurately fire the weapon.
The carriers straps are what you’ll most likely notice although once you’ve trained with it becomes a non issue, at least it has for me.
Get the proper sized plate / carrier and wear them correctly in training and I think you’ll find you quickly adapt to where they just feel normal.
As far as the cut goes, none of my plates are swimmers cut even though minimal weight is my top priority. I have a lot of other crap to carry and it’s in conjunction with soft armor which adds it own bulk.
Thinking it this way. If you want slightly more room to squeeze your shoulders together and have no real fear of ever being shot at while doing so you can save some ounces with the swimmers cut in the right carrier.