What is the difference between the two?
SMA is an account managed for a single (generally large) client. Mutual Funds pool the funds from a number of investors. Essentially a discrete mandate versus a pooled trust. Theoretically they could have the same underlying investments, however due to the nature of the relationship the detail reported to the client/s will vary; the discrete mandate should list all of the individual underlying securities, whereas investors in the mutual fund will simply see an investment within the pooled trust.
Generally, investment mandates don’t have to list underlying securities (though they will show up on your SMA account statement, unlike your brokerage statement for an account holding a mutual fund). However, SMAs do need to give the client the ability to determine (to a reasonable extent) restrictions on what may be in the account. Under U.S. law, that is defined in Investment Company Act Rule 3a-4 (https://www.law.cornell.edu/cfr/text/17/270.3a-4). Basically, the SEC in making the rule was looking to avoid SMA managers from providing unregistered funds by buying all the same securities in multiple SMAs.