Can whole pablanos be frozen whole?
Yes, you can, but ideally you should roast them first. I would peel them as well. You could leave them otherwise whole if you wish, to give you greater versatility when you defrost them. If you roast, peel, de-seed, then freeze, you could even make a passable (not great, but passable) Chile Relleno out of the not-quite defrosted pepper. Stuff and bread them while still partially frozen and they'll be easier to work with.

Here's an article on the subject from The Kitchn.