Why YSK: When you cook meat, any water on the surface must first evaporate before much browning can occur. You want to get as much of a Maillard reaction as possible in the limited cooking time you have before the meat reaches the correct internal temperature. Removing the moisture first means that the heat of the cooking surface isn’t wasted on evaporation and can instead interact with the meat to form the complex sugars and proteins of the Maillard reaction.
It absolutely should, looking back at my post I’m not sure why I worded it like that, but it will improve cheaper cuts. Your mileage may vary and you still want to do a good job actually cooking the steak, but the salt will do exactly the same thing. As it travels through the interior of the steak it will season it deeply, meaning every bite it properly seasoned, not just the surface. Meat loses moisture during cooking as high heat tightens the muscle fibres, squeezing out liquid. The salt will loosen muscle fibers, which squeezes out less liquid. Apparently some of those proteins also break down into a gel like liquid which clings onto the meat better. All of this I would imagine is actually probably more beneficial to cheaper cuts.
If you know you’re eating steak tomorrow, prep it now! In fact, I have always left it for 12 - 24 hours, but depending on how thick the steak is, a couple of hours is probably fine and will be better than not doing it at all. Just be sure the steak has reabsorbed all of the liquid that the salt drew out in the first place.