The CMS 1500 option is what you would generally use for printing a claim form.
Generating the paper claim using this option would open up the information to the PDF viewer software on your computer with only the text and without any borders or lines. The red-lined form (CMS 1500) would have to to be placed on the printer tray before giving the print command to have the text printed to the corresponding boxes on the red form.
HCFA-1500 option would show the claim information along with the lines and borders on the PDF viewer. On the PDF viewer the information would appear similar to a printed paper claim form.
The option is typically used for viewing the information that would populate to a printed claim form. This option is not to be used for printing and mailing. If insurance or a party requests you to fax the claim form, you can use this option to print it to a white paper sheet and fax them this sheet.