Dynatrace's OneAgent is able to monitor all outgoing network connections no matter if they are going though a proxy or through a firewall.
Unfortunately, there is no way right now to fetch any F5 firewall metrics right now, but we are working on a way to do that.
Maybe you could also tell me some details about which metrics of F5 and Google Search Appliance you would be interested most and what use-cases you wish to cover with them?
Plugin for F5 load balancer is in EAP program (or at least it should be by now). Please contact @Michael L. or your local Dynatrace representative for applying.