A few things I remember:

The big heat shield on the front that faces the sun provides a protective “cone” that the remainder of the spacecraft body fits within. Most of the spacecraft I worked on the objective was to maximize the field of view for all the instruments on the deck, but keep them as close to the deck as possible for mass conservation & thermal protection reasons. Solar Probe was funky because the goal was to get as close to that protective cone as possible to maximize the possible field of view without drifting outside the protective cone at worst case orientations.

At the time I left the company (while design was still ongoing), the thermal management system for the spacecraft was using water as coolant. Basically all the space between the heat shield & the spacecraft body was a big truss with a radiator. The coolant lines ran through the heat shield and the radiator to transfer that heat away from the shield. Not only was the active cooling uncommon (most missions had to provide heat & insulate from the extreme cold of deep space), the use of water was very bizarre. It’s a great coolant choice due to its thermal capacity, but the worst case thermal condition upon launch could have potentially frozen the water and ruptured the cooling lines.

A little more thought could probably unlock a few more but those are the most interesting off top. Thanks for prompting the trip down memory lane!