Hmm... I'm not sure I want to print both. We'll see.
The "skip frame" setting is basically just there because if very few motion vectors were good, Deshaker probably got everything wrong so it's probably best to skip the frame completely. There are many ways to deal with big moving objects depending on how big they are, how fast they move and for how long they're in the picture. Skipping the frame completely should only be done as a last resort, or if you're lazy
Quarter scale indeed means that the matching occurs on images that are reduced to 1/4 of the original width and height, but the accuracy is usually better than 4 pixels anyway for two reasons:
1. I sort of use sub pixel accuracy when calculating the best shift for a block. (I do this by fitting a 2nd degree function through the best shift and its two integer neighbors, and their "match probability values", and take the shift where this function has its max.)
2. Any impreciseness in the block vectors will be evened out when I combine them all for the total motion of the frame.
That said, I don't really recommend using quarter scale anyway. Personally I always use full scale.