It depends on the writers really. You can have the dedicated 1 on 1 relationship, but sometimes you can have multiple as well. It's all up to the person playing the mentor as to how many apprentices they want.
thinking about it just in canon would the rule of two apply yet? Bane in new canon lived like a thousand years before prequel stuff so a one-to-one ratio would work if we're just going off that alone. idk. what Gamov said is probably the best answer.