white always looks great with 30's repro's...
and the number of fabrics is certainly your (personal) choice)
some of us will tell you the more the better
if you like scrappy's----a different fabric for each bowtie would be awesome.
if you are not so much....a scrappy lover---you may find only 4-6 would be better suited to your taste.
depends on the layout you are planning too-
that part you have to decide on- on your own- we can't decide for you what you like...
but white is a great choice for backgrounds