For these two characters they will have the voice of a 3rd/4th grader of course, high pitched and loud as kids tend to sound. But each character sounds different so I hope you have the range to pull it off.

Chester: Chester is the more energetic cat in his friend group. He is a charismatic and loud cat, he's extroverted and loves doing crazy things for the sake of it. He's the average kid type but a little energetic and a little rebellious. He would sound very energetic, loud and excited all the time. But his tone is able to shift every time he doesn't get his way. he would sound like an average little boi but a little low pitched to make the characters sound different from one another.

Bub: the reason I added Bub here is because he doesn't really do as much as Will and Chester. I'm looking for someone that also has good range to act as separate characters. Unlike Chester. Bub is a more relaxed and relatable cat to have around. he is the more rational type and he always thinks before he acts, he mostly just sits around and says funny things to lighten the mood. He doesn't care for attention as much as Chester, he is just happy to be included. Bub would sound very relaxed and peaceful, and gentle. But he is no pushover so from time to time he sounds serious and firm