Transferring any single stitch to the adjacent needle will create a loop in that empty needle on the next pass of the knit carriage, and form that loop into a completed stitch on the second KH pass as it travels back to its original position. There are some constants in knit fabrics. For example, in lace, if all transfers are made in one direction, particularly in meshes, the fabric biases. Great if you want a bias fabric, not so if the original plan was to produce a balanced one. The cure: to alternate the direction of transfers sequentially, or in series. If done in series the result is a vertical zigzag with movement in the edges of the fabric to echo the bias direction in the knit.
If two adjacent needles (or more) are left empty, the first KH pass will create loops on those same needles. Without the knitter’s intervention and manipulation of at least some of those loops the space rather than creating holes, will be producing “ladders”. Ladder fabrics whether in combination with lace holes or not can be interesting, often involve hand techniques to make them more so, but the topic of the moment is transferred lace.
For knit stitches to form in/with the single second pass of the knit carriage, at least every other needle must have a loop or stitch on it. If two adjacent needles are empty one of several ways to achieve a larger round hole is to knit the first row, drop off one of the 2 “loops” created, continue knitting; this technique will create a secondary smaller hole in the fabric, it is a matter of preference as to whether this effect is acceptable.
To avoid a secondary “hole”, the method I prefer is to insert a one-eyed transfer tool back to front through the dropped off yarn, twist 180 degrees either direction, forming an “e”, and rehang the twisted stitch on the empty needle, thus “casting” that stitch on. This technique is sometimes used for buttonholes (not the best for that purpose). It is one way to bring the familiar e wrap used at the beginning of some knits into the body of a swatch/ garment. As the second knit row is completed the larger, “round” hole is now achieved.
In “automatic” slip small slits/holes appear where sequential rows of knitting occur, creating secondary patterns (seen in doilies).
It is up to the knitter to decide which trade-offs are acceptable ones. “Automating” functions add to design time and sorting out modifications to repeats but can speed up the final knitting process and facilitate accuracy when one transits from swatch to garment construction.
Lace cards can be planned to incorporate some larger holes, adding hand techniques to the mix.
And then there is the purposeful loss of holes, ie. in fine lace where the yarn is not transferred to but rather shared with the adjacent needle, creating a textured look rather than a hole filled one unless very thin yarn is in use.