It does not select a record type. Data for all record types are returned as part of the metadata. The create mode simply has the effect of excluding formula fields from page layouts and setting the "editable" flag appropriately for each field (some fields can be set on create, but not on edit). There is metadata that includes all the page layouts, and all the record types, and how they're mapped to the user. Your code will need to decipher this information to render the correct UI.
Edit: Based on your edit. It's not clear how to use create mode with recordIds. Providing an empty ID (e.g. 001000000000000AAA for accounts) should be sufficient, but I can't seem to find any concrete documentation. I'll have to test this and come back, or maybe you'll get another answer in the interim.