Sizing the AWAF

I would reach out to your F5 account team, they have access to tools to do a good AWAF sizing.

F5 SE's for the win everytime. You have hardware (rSeries) and VE's to consider and there are many other considerations to take,

But if you are looking at VE's this may help.

https://my.f5.com/manage/s/article/K14810