4%
This Low% category is the least number of item pickups that a runner can complete the game with.
It is possible to finish the game with an item percentage shown at the end of the credits of 0% by removing items that Samus previously picked up, but that category picks up significantly more items overall.
No run has yet been completed specifically for this category, although if this category is defined by the number of items picked up, all single-file 3% runs qualify, with Sniq's 26:15 being the current World Record.
Route
The route for this category is identical to the single-file route for 3%, except there's no need to do a Ceres Reset to remove the missiles from your inventory, so the Out of Bounds navigation at the end can be the same as Any% Glitched instead, just to set the Escape flag.
For the doorskips and ensuing out of bounds navigation, there are two methods, each of which have their own pros and cons. The method shown in the 3% tutorial uses easier out-of-bounds movement, but the out-of-bounds is normalized by starting the game from a Parlor save, so failing the doorskip and entering The Climb requires a reset. The other method, shown in the doorskip tutorial for Any% Glitched, normalizes the out-of-bounds by entering The Climb, so each failed attempt costs little time, but has much more difficult out-of-bounds navigation.
The third doorskip, as shown in the 3% tutorial, can be replaced by an X-Ray Climb, but given the lack of Super Missiles, you cannot use the standard Any% Glitched method to get stuck in the door. Instead, you must use the geemer at the bottom left of the room, since that is the only one that moves clockwise around the room, and does not move when off-screen. If you normalize your position with a series of turnarounds, that will allow you to damage boost off of the geemer and get Deep Stuck in the door. This method is significantly slower than an ideal doorskip, but it is much more consistent.
Collected Items
The items that make up 4% are the following:
Morphing Ball is required to 'awaken' the planet and utilize Power Bombs.
Similarly to above, one Missile expansion is also required to awaken the planet.
Powerbombs are required to open orange doors and destroy other destructible surfaces that block the way. They are also required to collect x-ray.
X-Ray Scope is required as it is an integral part of most of the out of bounds navigation, allowing Samus to x-climb into the out of bounds areas of certain rooms but also to modify the BTS of blocks and create whatever blocks are necessary.
Tutorials
Currently, the best resources for learning this category are this 3% video by SUPERMETROIDFTP and this 3% tutorial from Matrick. The newer doorskip method can also be learned from Zeni's Any% Glitched tutorial.