Based on this link (Combining Trained Models in PyTorch - #66 by rudascience), outA and outB are collected after FC layer. Because of this, my first question is answered.
Following with this post (Combining Trained Models in PyTorch - #68 by rudascience), it seems like I only need to define an optimizer and push to classifer.cuda() for classifer instead for both 3 models (i.e., modelA, modelB and classifier) ? Is this true or am I missing something in the post?