Best Practice for Using the Convert Lead Flow Step (aka Creating an Opportunity)

When you use the Convert Lead Flow step it will convert your lead to a Contact and create a new Account and Opportunity.

Marketo unfortunately cannot convert the Lead into an existing Account, because it can't determine automatically which Account to convert the Lead into. Thus, I don't recommend using this Flow Action, as it will create duplicate Accounts. To convert leads, the Marketo user profile will need the ability to convert leads, create contacts, accounts and opportunities. I recommend not giving Marketo these permissions. Convert leads is not actually a required profile permissions for the Marketo sync.

By the way, when Marketo creates the new Opportunity there is no way I know of for Marketo to assign the opportunity to a specific record type.