Which “instruments” should I pick to get this setup
TIA
It depends. If you know that the piece will stay in two staves throughout, either choose the Choir (reduction) instrument or, if the staff names are important to you, get a mezzo and a baritone and rename the players by hand.
On the other hand, you can choose the 4-part Choir (SATB) ensemble and then use Condensing to get back to this setup.
I would just use a Soprano and Bass, with altered staff labels, and a 2nd voice for the lower part on each line.