Quick check here:
If I have a field called Marketing Group on the account object. The same field is on the Contact Object, as a formula field to read from the account field.
A flow step from Marketo will NOT be able to change the value of that field if the record is a contact, correct?
If the record is a lead, the flow step can change the value. However, what happens when the lead is converted to a contact? For the scenario where there is an existing account and for the other scenario when it is a new account?