NOTE: RNG manip only seems viable using the Vaus controller and its more precise movement, since moving with the regular NES controller only seems to let you adjust the x-position in units of 3.

There are two or three possible x-positions you can be in to trigger a "Break" (level skip) spawn when hitting a particular item block.

0008 is the RAM value for your x-position, and the range of x-positions to trigger the Break item is:

08 18 90 A0

augmented by some amount? (+ or -)

Note that your actual x-position can't be less than 10, or greater than A0, which means that all four of these positions can't be simultaneously possible and therefore you only have 2 or 3 options depending on what value it is augmented by.

For example, in Stage 1 if we start with the paddle as far left as possible, after the ball launches we can reset the x-position to any of the following to spawn Break:
17 8F 9F
which appears to be the original range shifted one down (with the lowest value cut off from the paddle's actual movement range)

I can manipulate this in real time by setting the Vaus controller to an above value in advance, starting a new game with just the regular controller, setting up this position, then switching the Vaus controller back in while paused.

Now here's a ridiculous hypothetical situation:
Imagine you had 144 Vaus controllers, each preset to one of each possible x-value.
(Actually you only need 143 since one can double for both 10 and A0)
Using an emulator, you determine what x-values the paddle needs to be placed in to manipulate every Break spawn possible.
Then, using pause buffering, you repeatedly swap controllers out every time you need to move the paddle.
Doing this, you could RNG manipulate the entire game.
Of course this is kind of insane which is why I want to figure out exactly how the RNG works so I can try an intermediary strategy where I can calculate what pixel I need to be on right before I hit an item spawn and do my best to place myself there with pause buffering and background pixels.

As for what value the range gets augmented by, I'm not sure what determines this yet.
Possible factors:
Ball's x-position
Ball's velocity
Ball's movement (angle + direction)
# of bounces / ball's current velocity