Gosh! So many different opinions - and the heart problem thrown in as well! No wonder you are in a quandary.
What a bugger that everyone has something different to say.
I had a lumpectomy, breast conserving surgery with immediate 'tidy up' - and 15 months later, have minimal scarring. My surgery isolated the nipple & everything was removed (including sentinel nodes) from under the skin & then the skin trimmed & nipple sewn back in place, with some of the excess fat from the breast filling up the hole from the tumour.
Mine was also the right hand breast. I had radiation for 4 weeks - 20 in total, with the last 2 being 'boosters'. I had mine 'prone', so lying face down, which allows them to target the area very specifically, specially if the tumour is close to the nipple. I never ever thought that I was 'big breasted' - only ever having been a size 34! However ... I stopped wearing bras decades ago & I guess my boobs 'stretched' a bit (I never had kids!) so suited the prone position. The prone position also prevents the radiation from affecting the heart & lungs too ..... something I was grateful for.
I don't envy your choices - hard to understand why everyone has a different opinion. Have they explained WHY each one has that opinion? Maybe record it & let the other specialist hear it!!
I hope you have someone with you in these discussions, as they may pick up on a detail that you could miss in the stress of the discussion. Can you record any discussion for your own record? I do.