Hello LJD
The Swiss Travel Pass e-ticket is not everywhere recognised and must be exchanged for another entry ticket. Thus, it does not make a big difference whether you show the e-ticket or the paper ticket.
The only advantage in having it as an e-ticket: you can store it on your phone, or you can reprint it as many times you want.
The Swiss Travel Pass from the counter is a paper ticket and is not replaced in case of loss.
Both passes, the e-ticket and the paper version, do require your physical passport or ID card when using it (no paper copies, no photos on your phone).
Kind regards,
Roland