Tested and confirmed in 1.14.2.
Same behavior as in 1.13.2
Tested and confirmed in 1.13.2
A player's health will reset down to 20 if a health_boost effect of equal or greater amplifier is applied to them.
Sorry, I did search before posting, but did not see the duplicate.
Something in this description of the disabled flags isn't quite right, and it is possible to disable the mainhand, despite this report claiming you cannot. (The information on the wiki is mostly correct here https://minecraft.gamepedia.com/Armor_Stand/ED)
DisabledSlots:1 Prevents adding/replacing a hand slot
However, it seems that DisabledSlots:16 does not function as the wiki states (which may be due to incorrect information rather than a bug, I can't tell). While it seems like it should disable adding to a head slot, it instead disabled removing from the head slot, behaving the same as DisabledSlots:4096
It may be necessary for someone to examine the actual game code to figure out the algorithm behind this feature.