YBN is the format used in GTA V forexternal static collisions. Theres two types of YBN:
with low details name.ybn
and with high details with hi@name.ybn
About naming of collision files -  theres no need to name it as name_col.ybn suffix _col usually was used for begginers to better understand where to put collision in metafiles instead of using same name as ydr.
But anyways you can name collision whatever you want it.

Difference in static collision from embedded is:
1. Its separate file from ydr (no shit mr sherlock)
2. Embedded is placed on map by setting coords for ydr in ymap but for static collision coords are placed in 3dsMax.
3. Embedded collision is used mostly for small props but static collision is used mostly for big props, whole maps and regions.
4. In static collision are visible tyre tracks but in embedded not
5. With static collision you can make swimmable water with embedded not.

Generally for making maps is recommended to use static collision instead of embedded.

Heres example of creating embedded collisions in video tuts:

In creating static collision same as in embedded important is hierarchy, flags and Unk VertOffset
Collision Flags for general objects/terrain:
Flags 1
- Map Animal
- Map Cover
- Map Dynamic
- Map Vehicle
- Map Weapon
Flags 2
- Animal
- Animal Ragdoll
- Forklift Forks
- Glass
- Object
- Ped
- Plant
- Projectile
- Ragdoll
- Test AI
- Test Camera
- Test Script
- Test Vehicle Wheel
- Test Weapon
- Vehicle BVH
- Vehicle Not BVH
For stairs add stairs in Flag1- but dont add stairs flag to ground cuz it will change moving animation for player

Collision Flags for water:
Flags 1
- Map River
Flags 2
- Test AI
- Test Camera
- Test Script
- Test Vehicle Wheel
- Test Weapon

+ See Through
+ Shoot Through FX

For Unk VertOffset use 0,002 but if collision mesh is simple with small amount of vertex then use 0,02

And hierarchy:
All primitive collision must be under collision with mesh modifier. All collisions with mesh modifier must be in one line under composite:
Wrong hierarchy is most common issue after editing vanilla static collisions with primitives - example:
Usually its when user edits primitive collision (cut hole for door for example) and after edition its not primitive collision cuz its changed to editable mesh so user must add mesh modifier to it and move that edited collision part higher in hierarchy (collisions with mesh modifier in one line - it cant be under other collision with mesh modifier)