Heal strike can be annoying. At least many of the older panniers were more or less triangular shaped on the rear to allow them to be big at the top and small at the bottom.

I kind of approximate the rear triangle of my bike as the Do-Not-Load zone.

It is sometimes awkward, but one can usually figure out how to throw one's leg over the top tube, and not behind the seat. Perhaps that would be an advantage of a lower top tube. However, it is never that big of a deal.

I am now doing essentially 100% of my shopping by bike. So, all kinds of "crap" comes home with me either in a back pack, or tied to my rack. I've carried a few bike wheels home tied to the side of my rack. My Colnago might choke with it, but I had two, 50 lb bags of flour on the rack of my Cargo bike. And the trailer can pick up a lot that the racks can't handle. Of course, there is touring too.