Is dragging the only way to apply effects / presets to a clip?
Are there no keyboard methods / shortcuts to do this?
CTRL-D for the default transition. Everything else (effects and transitions) needs to be dragged.
As Harm says, there is only one, the Default Transition (that can be changed).
The closest that one can come to semi-automation would be to drag any/all Effects to, say the first Clip, and make any settings changes there. When you are satisfied with the Effects and their settings, Rt-click on it an choose Copy. Select all other Clips to which you would want the same Effects and settings applied (Lasso'ing them will work in most cases) and once Selected, Rt-click on these, choosing Paste Attributes. Done.
Consider the number of Effects that ship with PrPro, plus the common ones that folk add. There are no enough possible key combos to cover half of them, even if you remapped everything to just Effects. Unfortunately, PrPro (unlike PS) does not do scripting.