" I guess, I was mostly having gaps in mind"
"I wasn't sure how to deal with them after I sand the floor."

Proper floor sanding is an art, Edgers especially, can eat a heck of a
recess in the floor in a hurry.

Back in the "Old Days", they used paste wood filler on hardwood floors after
sanding, smeared it on heavy and wiped it up with burlap across grain.
Haven't heard of that being done for 40 years.

"Sanddust is the dust produced by fine sanding "

I would not use this, as said above, it will finish out very dark, like dirt
in your gaps.

Walt Conner