The 737 has 6 spoiler panels on each wing (12 in total). The outer and inner panels on each wing are ground spoilers and the 4 middle ones are flight spoilers. The panels are numbered from 1 to 12. Starting on the left wing the outer is No1 and counts sequentially across to the outer panel on the right wing as No12.
The ground spoilers are therefore 1, 6, 7, and 12.
The flight spoilers are numbered 2, 3, 4, 5, 8, 9, 10, and 11.
On approach the speed brake lever is positioned to the 'armed' position for landing. For auto-deployment on landing, the airplane must be less than 10ft RA
(Radar Altitude) and the Thrust Levers in the idle position.
Upon touchdown and main wheel spin-up on any 2 main wheels the speed brake lever is automatically positioned to UP
and all flight spoilers extend.
The ground spoilers will extend when a mechanical squat switch on the right main gear strut is compressed during the landing phase.
Therefore it can be deduced that in the landing on the video, the pilot landed on the left main gear first followed shortly afterwards by the right gear.
It is true that the spoiler panels deflect to different deployment angles.
On the ground when the speed brake lever is manually or automatically fully extended - the ground spoiler panels 1 and 12 extend to 60 degrees deflection, and panels 6 and 7 extend to 52 degrees. Flight spoiler panels 2, 3, 10 and 11 will extend to 33 degrees and panels 4, 5, 8 and 9 will extend to 38 degrees.
In flight if the speed brake lever is positioned to the maximum in-flight detent position, spoiler panels 2, 3, 10 and 11 extend to 20 degrees deflection and panels 4, 5, 8 and 9 will move to 22.5 degrees.
Ground spoilers do not extend in flight.
Of course flight spoilers are also used to aid in roll control and will deflect on the downward wing according to inputs from a spoiler mixer. This shouldn't be confused with operation of the speed brakes
Hope that helps answer the question.
With regard to hydraulic supply.
SYS 'A' powers panels 1, 2, 4, 6, 7, 9, 11, and 12
SYS 'B' powers panels 3, 5, 8, and 10