The one that appears on the very left on the first page and that connects all the staves.
(Trying to make my own custom manuscript paper with Dorico. 
)
Yes, as long each system only contains one stave. See https://www.steinberg.help/dorico/v3/en/dorico/topics/notation_reference/notation_reference_barlines_systemic_after_first_system_hiding_showing_t.html
There’s been a thread on ways to do this.