I think wearing sunglasses is a perfectly good idea. It adds to intimidation, as well as makes it so that your opponent doesn't know where your concentration is. It adds a mental advantage to you, and as a chess player, know that it also can keep your opponent from second guessing you. In Chess, players are notorious for staring at pieces or flaws in the position that they are worried about to think ahead. It may not be as big of deal in Pokemon but it can be an edge. Also, there is an advantage to sometimes letting your opponent see a card in your hand. Doing this, you can trick them into certain moves. For instance, lets say a certain attack they use would be extremely effective if you don't have a Switch to recover with, but even if you do, you know your hand isn't going to recovery well. Showing them your switch will certainly discourage them from making what would still likely be the best move.
Also, lets say you have a 5 card hand. They wonder if you have a key card, like an evolution, or rock tm. "Accidently show them all but one card, which is intentionally the card you want to keep hidden. By making them think theres a 1 in 60 chance of you having that card ( If you can keep up the mask that you showed them on accident ) than they will be much more likely to play as if you don't have said card. Its much like the simple idea of moaning all game about how you wish you ran Rock TM, than once they drop all their evos with Rare Candy, drop your Rock TM and win the game. Its also fun to complain about your opponent having a certain card, hoping they use it against you in order to give you a win. I've never been more amused than when I complain " Let me guess. You TDed the stupid Gardy EX didn't you " and than watching them drop it on me, only to retaliate with Rayquaza, Firestarter x3, Multi, KO, GG. You can trick your opponent into making alot of mistakes by making yourself seem helpless, and at times showing a few cards inconspicuously can be extremely helpful. The sunglasses also help in hiding your emotions when doing said tricks. None the less, 99% of the time glasses just add intimidation, nothing more.