16 Foot Bartop

As dumb as this sounds I think the best thing to do is lay out the plywood at the store. Try to pick two sheets that match or should I say the grain patterns look natural together, even if you have to offset the sheets and waste some material. In your case, you want the top to look as if it was one piece not two joined.
You don’t have much choice but to butt joint the ends seeing the total length is 16 ‘ and each sheet is 8 ‘. What might help is if you buy a tinted (coloured) oil based paint crayon that matches the colour of the red oak grain. Remember to match the colour after the stain is aplied if doing so, stores always have examples of finished product on wood samples. What this will do is allow you to do is colour in to line up or add grain for the affect of one piece if needed. Don’t go overboard as it then may be obvious what you did. Perhaps testing on two scrape pieces first then finishing will help determine what amount or methed gives the best results ?
Might not be a bad idea to help the glue bold the ends tightly together by adding (glueing and screwing) a small piece of plywood which overlaps each end under that area from the bottom side. But add this piece once the top is in place so you know if any obstructions or the size is limited.