Address Envelopes AGAIN

If you are addressing an envelope to a friend and their date, knowing their dates name (live in, fiancee, etc)

would you use one or two lines. Would you put the girls name first if you are friends with the girl and the guy is her date?

Also, what do you use for apartment number.
#3B or No. 3B

Example #1

Ms. Jane Doe & Mr. Bill Smith


Example #2

Ms. Jane Doe &
Mr. Bill Smith


Example #3

100 Main Street #3B

Example #4
100 Main Street No. 3B


or does it just matter how it fits on the envelope?

I put each name on one line
Ms. Jane Doe
Mr. Bill Smith

My lady said that Number or apt should be written out & I would put names on same line.
Joe Smith and Mary Smith