Is it possible to deploy or register a workflow from say agent 1 to run on agent 2? Do I need to log into host with agent 2 and register/deploy the flow from there?

You can as long as you use flow Storage available to agent 2 to find the Flow. The default is Local storage which doesn’t really let you run on another machine so you have to specify what to use

then, it's a matter of changing the label on the run config