Many questions about control rig

I’m maya user and I’m using unreal engine’s control rig to rig a Mannequin.
I follow these steps from Unreal Engine Control Rig tutorial(outdated-ref official unreal channel for new process) - YouTube.
It is basic but I have some questions:

1.get joint transform’s type has four ways, and I wanna know what they means can I add controller in the viewport,so I can move model with controllers in the viewport not in rig graph

3.Everytime when I click compile,Mannequin will be back to default pose ,how can I set the default pose? to add parent constraint etc?

If you have any ideas,igging information about unreal , tutorials, please let me know

thank you