I've built a few boats from plywood stitch and glue.
I used epoxy for the connections but did not coat the plywood surfaces with epoxy and glass because of the increase in weight. I painted and clear finished the plywood. I have owned and used the boats for many years and I've not once regretted leaving out the epoxy coating.The hulls get the odd dent and scratch but are easily fixed with filler and paint at the end of the year. The boats seem to be strong enough without epoxy and glass coating
I've built several small plywood stitch and glue boats during the last 12 years.
I've never coated the plywood with epoxy and glass because it makes the boat much heavier. I use paint and varnish. I use the boats on lakes and they frequently contact sharp rocks. I have not encountered a situation where I regretted not having the extra strength. The boats are strong enough without coating and the inevitable dents and scratches are easily repaired. They're also cheaper and quicker to build
Why do designers specify epoxy and glass coating?
and much easier to carry.