Both the size of the pot and size of the plant affect frequency and quantity of watering. Smaller plants drink less, so they need to be watered less often. If small plants are in big pots they also need less water quantity at a time so they don't get "wet feet" while the growing medium dries out. Big pots take longer to dry out so you usually need to water them less often.
On the flip side, big plants drink a lot and need a lot of water at a time. Small containers dry out faster, so they need water more often. If you have a very small pot with a big plant, you want to completely soak the medium every time to help the medium dry out slower, but soaking the medium could kill a seedling in a big pot.
To add another wrench, smart pots and air pots (which get air from the sides) dry out a lot faster and need to be watered more often and more thoroughly than regular pots of the same size.
Additionally, the temperature, the airflow, the humidity, and the composition of the growing medium all have a big effect on how much water the plant drinks, and how much water evaporates.
With all the different variables, it's hard to come up with a "set schedule" that will work for every plant in every setup. That's why it can be so hard to get a solid answer to the question of how much and how often to water. It's important to give both the right amount and the right frequency to make sure roots stay wet but not too wet, yet that schedule is different for everyone!
