It is correct that the excel importer doesn't support xlsx. The library we use only supports the xlsx format since a few months and we still have to validate the all functions for an xlsx file are fully implemented. We know it's missing and we are going to make the excel importer compatible with xlsx but we don't known when thats going to be.
2 Your expectations are correct, when selecting the function "Build template from Excel" it should create a template with all the columns from your excel file in it.
Can you validate if the excel import is correctly imported (no empty javaactions, you use only replication userlib version 1.2)