1 party [person or family] per car....... and not that kind of party! Service for us was great in January. Stayed at BCVs and used it from IG to HS via CBR, both to and from. You'll run in to longer than normal wait times first thing in the morning and at HS/Epcot park closing times.
Yes, I was solo on my three trips during Covid, and was always alone in my gondola. I also saw CMs board with cleaning supplies and give the gondola ahead of me a thorough wipe down during the flight a few times, so they are cleaning during the day also.