Either would work, but regular plywood won’t give you a nice, smooth finish. I’d strongly suggest using 3/4″ oak finish grade or cabinet grade plywood. It will be nice and smooth and look great under the epoxy coating.
There are probably more ideas for similar bar tops that use decoupage techniques with photos, concert tickets, bottle caps, corks, hockey pucks, baseball ball and bats, rocks, tile chips, you name it! All encased forever in Envirotex. https://www.barplan.com/gallery
Do a search on the forum for ENVIROTEX.