This might arguably have gone under the Academia Forum as well, but since we're far more familiar with the fictionalized Jin Yong versions of these two historical figures and the actual historical figures themselves...
Obai and Ng 3 Gwai were probably the two gravest threats that Emperor K'ang Hsi faced during DOMD. Fortunately, he didn't need to face them both at the same time. By the time Ng 3 Gwai really became a problem, Obai was already long in his grave.
If Obai were alive at the time that Ng 3 Gwai started his insurrection, would Obai have sided with the emperor or with Ng 3 Gwai? On the one hand, Obai didn't hold the youthful emperor in much esteem. On the other hand, I doubt that Obai would have wanted to see Ng 3 Gwai usurp the Qing throne. Which side would Obai have helped?