Sounds like a good idea but screwed down boards eventually become much
harder to remove than nailed ones. They rust in unless you use brass ,
the slots get rounded over or filled up, they get jammed tight due to
board movement etc. Also screws look messy. Neatest and easiest to
remove are boards nailed with round lost-head flooring brads, if you
cut the boardtongues off before you put them down.
You wont need expansion gaps unless the area is very damp in which case
you've got problems anyway. New floor boards are usually cramped as
tight as possible but they always shrink a bit unless exceptionally dry
to start with.

cheers
Jacob

PS basic rule of good woodwork anywhere; never use a screw if a nail
will do. Nails are cheaper, neater, quicker and can be easier to remove
- or the item easier to pull apart.