Chairman Xi announced PLA restructuring as part of the 13th Five Year plan. The 13th Five Year plan reforms began in 2016.
The 7 Military Regions have been replaced by 5 Theater Commands
The PLA now essentially has 5 "services": PLA Army, PLA Navy, PLA Air Force, PLA Rocket Force, and PLA Strategic Support Force. The PLA Rocket Force is what was previously known as the Second Artillery Corps.
Xi ordered a reduction of 300K troops throughout the PLA, this is expected to have a larger impact on the PLA Army than the rest of the services. It is possible that there could be a 400K troop decrease within the PLA Army, and 100K troops are added within the other services. This would reduce the total size of the PLA (including the PLAAF, PLAN, PLARF, and PLASSF) to just under 2M.
Within each Theater Command there are usually 2 or 3 Group Armies. Each Group Army typically contains an Army Division and other Motorized Rifle, Mechanized Infantry, or Armor Brigades/Regiments. These Army Groups also typically have an Artillery brigade and a SAM/Air Defense Brigade, although the PLA Air Force handles the brunt of the Air Defense mission.
If I had to guess, the 150K troops moving near the NK border are an entire Army Group, parts of another Army Group, and support elements from the Theater Command in addition to PLAN and PLAAF units to support airlift and naval movement. It is important to note that the Northern Theater is not contiguous. Shandong likely belongs to the Northern Theater but it separate from the rest of the Northern Theater. This might require more need for PLA Navy assets to move bodies.
All this information (minus the graphic) is from The Jamestown Foundation report on the PLA Reforms and the order of battle stuff is from Wikipedia and GlobalSecurity.org
Another good source for PLA Reform info:
https://www.rand.org/blog/2016/09/pla-reforms-and-their-ramifications.html