Also adding to confusion is that different routes (and distances) have different hard products.

"Premium economy" on an international long haul flight is often the same (or very similar) seat as "first class" on a domestic flight.

I've recently been blessed with being able to afford flying on lie-flat seats (international business class). That said, I've found what you are calling "economy plus" to be the sweet spot.

You get slightly more leg room, but also priority boarding so that you don't have to worry about getting your bag gatechecked. It's also only slightly more expensive than main cabin regular economy.

"Premium economy" is significantly more expensive, and while you do get a bigger seat, it's not lie-flat. You can recline more, but the few times I've flown it, you are still able to piss off the passenger behind you when you recline with all the shenanigans that can entail. Thus I find it not worth the premium.