Need a Benchmark documents for F5 Advanced WAF or Big-IP or etc.

this is another one of those "depends" on what you are looking for questions.

this is best answered via -a f5 sales rep / sales engineer combination as decision will need to be made all of which can alter the solution.  
i.e. -  is the physical equipment ( on prem  / colocation)?  Is this virtual equipment (vmware / cloud/ vcmp).   all of which have limitations that can be found 

https://www.f5.com/pdf/products/big-ip-platforms-datasheet.pdf

https://www.f5.com/pdf/products/big-ip-virtual-editions-datasheet.pdf

What modules do you plan on using?   How many vips do you plan on configureing? 

The f5 is a swiss army knife of an IT tool set, it can do a amazing amount of work, but if its not properly spec'd out, you can end up as an unsatisfied customer.  A good sales team is your best option.