I just saw your location. Hopefully you’re all ok there in Napa. We could smell the fires way down in Richmond.
I thought this video on overheating and piston failure was interesting. My guess is that yours are probably not as bad as the ones shown because the failure was at idle rather than at WOT.
https://m.youtube.com/watch?v=aCr9iltAx2w
Could it be valve seals only? Small probability. Less than 5% based on the event that triggered the smoking. There are methods to change the valve stem seals with the heads staying on. I have not done that myself, but it looks easier than changing pistons. If you do it yourself it might be a good decision. But if you have to pay to have it done then the cost and risk trade off leans toward pistons. Depends on if you want to do it yourself or how tight your time is.
If I had lots of time and mechanical ability, I’d try the valve stem seals first, knowing it’s more likely the pistons, but hoping for an easy fix. If that didn’t do it then I’d dig deeper and pull a few pistons.