Pretty much, but when the contact point is off center, the direction of force is along the cueball's initial direction (i.e., it differs from the cue's pre-impact direction by the squirt angle).
Very true (but the operative word is slightly). However, for a given desired cueball direction, I think it's pretty clear that you can generate the same amount of spin with either method...and with the same miscue limit (see Patrick's diagram linked to earlier).
Hu, I don't think the numbers bear this out. They show that for a moderately hit cueball (approx. lag speed), while applying half of maximum english (1/4 radius tip offset), to get enough sideways speed on the tip before contact to merely negate squirt, you'd have to accelerate almost the entire mass of the cue sideways - say, by flicking the wrist - to a speed approaching break speeds, and in a time period much shorter than it normally takes to get a cue up to break speed. And the only gain in spin from this would be the slight difference in going from squirt to no squirt (a percentage point or two), which also means the line of force would be only slightly different. At greater tip offsets, greater cueball speeds, or to generate substantially more spin, the task becomes even more daunting.
And, after all that, you're still limited by the miscue limit, which is limited by the coefficient of static friction, which limits the maximum spin/speed ratio, which is the same no matter what method of attack you use.
Jim