I've generally been 200# plus. 190 for a short while.
I had a Columbus SP frame built for me. I was on tubulars. It was not comfortable. I ride tubulars now. My son trains on tubulars - now, on carbon frame. Tires matter, but it is not the tires.
I had several others and road about 20 (my job) and it was more the frame builder.
My Raleigh 753 was very comfortable.
I think it is:
-Material - tubing thickness
-Geometry
-Joining material. Brass vs Silver.