I've done PBP with and without. I prefer without.
In 2011 when I got to my drop bag I wasn't ready to sleep, so I changed into my fresh kit and rode another few hours. At the sleep stop I showered, put my sweaty clothes back on, got to my dorm bed, stripped under the blankets, and slept nude. It was not ideal.
In 2015 I also had a drop bag. I got super sleepy early, and ended up sleeping way before plan, on a cafeteria floor. When I got to my drop bag, I showered, changed, and rode on into the night. It work out okay.
In 2019, I carried my stuff. There was no stressing over what to carry and what to pack. The headwind screwed up my schedule, but since I had my gear I slept when I felt like sleeping, showered when I felt like showering, and changed when I felt like changing. It was nice.
For sleeping on the road, I carry a foil blanket. IIRC, I've used one twice. Otherwise I've slept in controls.
My favorite 1200k approach is to ride fast and sleep lots.