Is a x2 leg a pick up n dump or a spear?

Like ive been watching GSP and I swear sometimes he just dives head first at their legs to take them down (usually when they try to punch him)

Ive seen demos of how to do a x2 leg and it says take a deep penetration step keep your hips under you and lift them up, then dump them.

Ive seen some guys run head/shoulder first into their hips while pulling their ankles/ lower legs towards them.

And I swear I see guys just diving for the legs like a spear aiming to go through them to flatten them with forward drive while holding the legs so they cant take a step backwards.

Am I just seeing guys do a standard x2 leg just really fast? Or are these all worthy takedown techniques?

I'll take a stab at this.
Perfect double leg technique would be level change, penetration step, head on the side, arms around both of opponents legs at the knees, trailing leg comes through as penetration leg comes back up to the feet, drive sideways with head pressure(not straight back )which prevents the sprawl.

That being said, technique is rarely perfect in an actual match. Also an MMA double is different than a pure wrestling double leg because of the posture. The take down GSP does a lot is closer to a barzagar than a double.

In a wrestling match there's a lot of ways to finish a double once the initial shot goes bad. You can use the trailing leg to trip, switch off to a single, head between his legs and elevate him up, Iranian ect.

Sometimes just keep driving, it's not pretty but often works. That's probably what your seeing and calling a spear Phone Post 3.0