There is actually some interesting literature on chronotype diversity in cats, especially as it pertains to their food intake. From a 2019 study:

The general rule of thumb for adult cat hydration is 4oz water per 5lbs body weight, including moisture from diet (Cornell Feline Health Center).

Hello! Your cat's stool quality may change day to day, but any prolonged abnormal stool habits should definitely be escalated to your vet. You can qualitatively assess using a fecal scoring chart, like this one from Purina.