How to create Receivables Invoice faster

Hi!

 

1. How to reduce the time of auto invoice import program
2. Which one is faster receivable invoice api or ra_interface_lines_all in order to create invoice.
3. What is the difference b/w auto invoice import program and auto invoice master import program & what if I only use auto invoice import program instead executing to concurrent program, does it make difference, can we reduce the time of creating invoice this way
4. What is difference b/w ar_invoice_api_pub.CREATE_SINGLE_INVOICE and ar_invoice_api_pub.CREATE_INVOICE

Regards