Can I get EA Play for both my PC and PS4 with one subscription?

I would imagine it's more Sony than EA on this one...   When you sign up for EA Play on the Playstation store, Sony is keeping 30% of the subscription fee.  To transfer that to PC would mean EA is getting 100% of the signup, and Sony (or Microsoft, or Apple, etc) always have clauses in their contract that prevent you from starting a subscription in their ecosystem and then cutting them out of the cut later.  You could always do month to month EA Play and then move freely to whatever platform you want, but you'll pay a lot more annually that way.