If it's primarily a demo to get live gigs, the appropriate presentation is pretty much what people would hear if they saw you live. That's the by-the-book response.
And as such, if you have a friendly small-room venue that you could record a live show in with approprate audience reaction, that would be good.
If you have friends who MIGHT play with you on gigs, by all means get them to join you on the recording. Then you have flexibility when negotiating gigs "I can have that awesome fiddle player with me for $xx more".
And I don't think a modest overdub played by yourself is a sin. You want the recording to sound reasonably full, and hey, it's a showcase for your talent, so show em your talent.
There is no one answer, except to get the best live-sounding bed tracks you can, and you'll know if they need something more added.