Thanks for your question about formatting hymnals.
The most common method for transcribing the music for hymnals is using piano format with the right hand containing the soprano and alto parts, (intervals read downwards) and the left hand containing the bass and tenor parts (intervals read upwards). This highlights the melody and the bass line, but contains the inner voices as well. The lyrics would then come after the music, in 3-1 paragraph format, beginning with the stanza number and a period. If there is a refrain or chorus, it is a separate paragraph below the first stanza.
One could use open score, as if for a full choral ensemble, as shown in section 37 of the MBC 2015. Rarely would one do a hymnal with single voice parts done separately.
I hope this helps! Let me know if you have further questions!