The question about painting on plywood as a suitable surface to paint on was raised on a forum which I subscribe to.
I should think that plywood over a certain size would be unsuitable to paint on unless you strengthen the back of it.
I have painted on chip wood using oils some 40 years ago and it still looks good today. No warping on a 40 x 60 cm board 2cm strong (16x24in and 3/4in strong).
Even the chip wood panels which are only 1/2 in strong do not seem to have bent over the years.
By the way the back was left raw.
I suppose I can be glad that I was´nt into selling in those days otherwise how would I know
Plywood is a different story. I have never used any beyond 20x30cm at 0.5cm strong. I would be reluctant to use any larger sheets for painting.