Layer3 mode Vs Layer2 mode

Hi everybody, one very large question for you:

 

 

Currently we use a pair of BigIp LTM behind our internet routers only to make the loadbalancing between two Webapplication firewall. So the bigip are in layer 2 mode and don't do anything more than loadbalancing. We would like to put the bigips in the layer 3 mode and maybe do the ssl offload on the bigip to add some headers. I saw very few informations about it in the documentation. What could be the impacts in our infrastructure, advantages-problems... Any related information about the layer 3 mode is welcome.

 

 

Thanks in advance.