Idk what rank you are, but if you're anything under ascendant I promise that if you learn Viper well you will have a massive advantage. She is THE goat smoke agent on Breeze, and every game I've played her on Breeze I've fried. If someone else picks Viper, go double controller and pick Astra/Omen.
A good starting setup on defense to learn with is throwing your wall to cover B tunnel and the rotate from mid to A, and throwing orb on B main. I usually start by holding an angle watching B main for info, and as soon as I see anyone I un-peek, throw up the orb, wait for them to try using flashes or other utility to enter the site, and then molly the entrance. If they wait out your orb before attempting to come into site, just hide and do your best to survive until your team can make it in with the rotates. If you need to rotate A, throw up the mid wall and cross. I usually like to molly the way that attackers can get to A doors through mid while I'm crossing too to try to prevent them from swinging through the wall while I'm going into A doors. If single controller on attack, use your wall to split either site that you're going to. On A, throw the wall from where the rope to go up to halls was through the center of the pyramids on A, and on B I prefer to send it diagonally from right before the elbow entrance to the back left of site (this is mainly so along with cutting off sight lines on site, you're also using your wall to smoke the elbow flank.) If double controller, just default your wall to the A wall and let the other controller smoke B, which will allow you to throw up your wall during the round to create pressure on A while your team might be slowly going B.
I hope if you do decide to learn Viper that this helps!!