The 'meet other team members' may be something they like to do, to get you to like them. Get an attachment to the potential employer. A convincer against other offers.

Multiple interviews are a red flag to me. They don't know what they want. Interview once and get very very deep. This requires a lot of introspective thinking knowing who you actually are, who your organisation is, and what's needed to be successful there. When that's done, a single interview is fine. Multiple interviews are a sign the organisation doesn't know what it is and lacks the substance for action.

As for duration: it could take as long as it takes. But all in one take, no reason for spacing out over multiple days.