Wynn and Sands said you have to wear a mask, Caesars and MGM said its "recommended". I'm guessing most players will be wearing them day one but you will be just fine going without.
The shields are ideas that have been demonstrated at a number of places, but they will be only here or there. The idea sounded good on paper, but when managers and potential customers saw them there was total horror so don't expect to see them much and for them to come down quickly. Another point that came out is only 4 people on a poker table. Almost no one will want to play 4 handed so don't expect poker rooms back any time soon.
Lastly, I don't think every other slot being shut down will happen much and won't last long. Acres built a system that can block neighboring machines from being played which is probably the best idea if they really want to keep people from playing next to each other. Otherwise, they can just ask people not to sit next to a machine getting played. If you say you have to turn off half the machines there will be pissed off customers saying you shut off my favorite machine or claim that they shut down the loose machines or the one that was about to pay off (all myths, but they still have traction with slot players). I don't think the gaming regulators thought that one through well.