I may be interpreting your question incorrectly, but it looks like you may be able to get your picklist values without using a snippet.
If all you’re trying to do is simply render your field as a picklist and limit the available picklist options, you can render your record type field as Picklist, then create a lookup filter on the record type field is not in the list of multiple specified values, and then list the names of the record types you don’t want to include.
Also, regarding part (2) of your question, RecordTypeId is a reference to the RecordType object. All record types in Salesforce fall into the RecordType object, and each has a field SobjectType which contains the name of Sobject to which the particular record type applies. So, like other reference objects in Skuid, the field uses an id to get another object, but it allows the user to look up an object by typing in its name, and it displays the field as the object’s name.
