After completing the Main Story, you can rematch the Champion Cup as many times as you would like. This time around, you can select which opponents will be added to the tournament or if you would prefer a random set of foes. There are twenty-six trainers you can face this time around, including Hop, Leon, Marnie, the eight Gym Leaders, and fifteen Random Pokemon Trainers. The Random Pokemon Trainers that weren't seen during the Main Story will usually focus on using one Pokemon Type (much like each Gym Leader), but their Pokemon will be at slightly lower levels and they cannot Dynamax any of their Pokemon.
Theemin is one of the fifteen Random Pokemon Trainers you can face when rematching the Champion Cup, having completed the entire Gym Challenge. Theemin focuses on using Steel Type Pokemon, having Perrserker, Mawile, Bronzong, Steelix, and Copperajah when in battle. All of Theemin's Pokemon will be between Levels 56-58, and, again, none of their Pokemon will Dynamax when in battle. Because of this, Theemin is especially weak against Fire Type Pokemon & Attacks. Theemin also struggles against Ground Type Pokemon & Attacks, since most Steels Types are also weak to them.
After defeating both the Isle of Armor and Crown Tundra DLC Packages, Theemin's Champion Cup Rematch Pokemon Team will now be between Levels 68-70.