1. Suction -- it hooks up to the suction side of your pump. Good but not very efficient. Will clean most pools just fine.
2. Pressure side - it hooks up to a return. Some require booster pumps but with a VS pump you can probably run any without the booster pump.
3 Robots Most efficient lowest operating cost. Most expensive to purchase.
I have a Polaris 360 pressure side cleaner that operates all the time.
If you don't mind placing and retrieving the robot once a week they do a great job and are least expensive to operate. Look at reviews on Amazon. There are plenty of models for all different sizes of pools.