Can I add my client or partner as a member instead of an admin to keep things secure?

Yes. When you invite someone from a business profile through Manage access, you choose their role, so you can bring a client or partner in at a lighter level rather than full owner access. Business Owner carries top-level permissions, while Collaborator and Partner roles let people participate on a deal without controlling the whole account. This lets you keep a client involved in their own application, or assign a partner to handle communication, while you retain control over the rest.