At around 18.20, the laser beam from Addison's console can be seen reflected in the lift (elevator as American viewers would say).
Despite being a hologram, Addison casts a shadow on several occasions, most notably when Ben leaps into himself in 2018 and bumps into Addison of the time.
At around 22 minutes the hologram of Jenn can be seen to giving off a shadow whilst running through the building with Ben.
Ben leaps to the future but not into the body of anyone. Ian specifically says he had trouble finding someone for Ben to leap into; obviously, he did.
Magic tells Ben that he always keeps a ballpoint pen in his breast pocket. Ben attacks Martinez (in Magic's body) and takes the pen from his pocket. The pen he takes is a felt-tipped marker, not a ballpoint pen.
Ben says it's snowing in LA, but it's not clear how he knew he was in LA. It is possible he recognized the Quantum Leap base, but it seems likely he'd have more of a reaction to that realization.
Janis says that the modern-day Quantum Leap team isn't becoming aware of changes to the timeline because altering their own personal histories has created a "quantum bubble." She says this hasn't happened before because they've never affected their own pasts before. In S.O.S. (2023), they drastically alter Addison's father's history, making it so he is never discharged from the Navy and never becomes the cold, closed-off man she remembers growing up with.