Final answer:
The type of fee-based account with the highest degree of customization is a managed account or wrap account, which offers personalized service and investment strategies tailored to clients' preferences and goals.
Step-by-step explanation:
A fee-based account that ranks highest in terms of its degree of customization is typically a managed account or a wrap account. These accounts are designed for affluent clients and offer a higher level of personal service. Clients with managed accounts can work closely with investment advisors to create and manage a portfolio that aligns with specific investment goals, risk tolerance, and preferences. In contrast to mutual funds or robo-advisors, managed accounts provide the opportunity for personalized investment strategies and may include exclusive access to certain investments that are not available through standard brokerage accounts.