“Hex Tweaks” are loosely defined as sets of single-or-multiple-byte-changes that can be preformed for desirable effects. There is no clearly-defined upper limit for the number of bytes that can constitute a 'hex tweak' but they are usually less than 16 bytes' worth of changes.
Tweaks for the mechanics of Samus.
0x1C2A - 01 to 02
0x1C6D - 01 to 02
Samus runs faster on the ground.
0x1C99 - 02 to 03
0x1CCA - 02 to 03
Morph ball rolls faster on the ground.
0x1CFB - 01 to 02
0x1D27 - 01 to 02
Samus moves faster in air.
Tweaks for beams, missiles, and bombs.
0x51A1 - Everything up to 0x51C1 becomes 04
Makes missiles fire at a faster and more consistent speed.
0x53FC - 60 to ??
Changes the amount of time it takes for a bomb to explode. Change this to 30 for Super Metroid's bomb explode time, or 20 for Zero Mission's.
Tweaks for energy and missile drops.
0x8270 - 05 to ??
Changes the amount of energy a normal energy drop will add.
0x82AC - 05 to ??
Changes the amount of missiles a normal missile drop will add.
Tweaks that don't quite fit in with any of the particular categories.
0xAA43 - 05 to ??
Changes the amount of missiles it takes to open a hatch.
0x190E - 56 to FF
Makes a spin jump fly upward forever if you release A before the apex of the jump. Hitting a ceiling or shooting will cancel it. Best combined with Respin.