Are There Any Benefits/Drawbacks to the Different Movement Types Besides Speed?

yes, they change

• reaction times
• visibility to enemy
• shooting accuracy

i.e. it takes more time from running to shooting than from walking to shooting

modifiers are added to any action performed in that stance.

cannot find the value for readying the weapon, but you can time that fairly easily in the game shooting at ground.

  1 standing
  - speed modifier  0
  - visibility modifier?  0.2
  - range of view modifier?  1.2
  - angle of view modifier?  1.5
  - doesn't require training yes
  - works without special equipement yes
  - accuracy modifier  1
  - size modifier  1

 2 walking
  - speed modifier  2
  - visibility modifier?  1
  - range of view modifier?  1
  - angle of view modifier?  1
  - doesn't require training yes
  - works without special equipement yes
  - accuracy modifier  1
  - size modifier  1

3 running
 - speed modifier  3
 - visibility modifier?  1.5
 - range of view modifier?  0.75
 - angle of view modifier?  0.5
 - doesn't require training no
 - works without special equipement no
 - accuracy modifier  1
 - size modifier  1

4 kneeling
 -  speed modifier  0
 -  visibility modifier?  0.1
 - range of view modifier?  1.2
 - angle of view modifier?  1
 - doesn't require training no
 - works without special equipement no
 - accuracy modifier  1.25
 - size modifier  0.75

5  laying
 - speed modifier  0
 - visibility modifier?  0.1
 - range of view modifier?  1.2
 - angle of view modifier?  1
 - doesn't require training no
 - works without special equipement no
 - accuracy modifier  1.6
 - size modifier  0.75

6 crowling
 - speed modifier  0.4
 - visibility modifier?  0.25
 - range of view modifier?  1.2
 - angle of view modifier?  1
 - doesn't require training no
 - works without special equipement no
 - accuracy modifier  1
 - size modifier  0.75

question mark for where I am guessing the in-game effect

size modifier changes also how cover hide you and how 'tall' you are in visibility checks (terrain line of sight matters)