Will filling gaps with epoxy in a new hardwood floor look ok?
The epoxy glue products are not made for this situation. It will stick out like a sore thumb.  It will not accept stain.  There are any number of good quality wood filler products that are made specifically for this application. The manufacturers of these products state that they will accept stain however, I have found that to be only partially true.  They are still the best choice for this job. Wood that is properly seasoned and good tight installation is the best defense against having to fill the cracks.