For a browser "remote end", I think all of the Processing Capabilities steps are irrelevant except perhaps for reading "acceptSslCerts", "proxy" and "pageLoadStrategy" and configuring the browser as required to set those. For an intermediary node which acts as a interface to many possible remote ends there are presumably semantic requirements on the other listed properties, but the spec doesn't really set those out and has strangeness like a vestigial "unmet capabilities" variable that is initialized but never modified.